Abstract:
An add-on safety lock that blocks lever rotation by bracing the lever against a fulcrum point at the handle shaft and nearby door structure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based on U.S. provisional applications 60/416,684 filed Oct. 7, 2002, and 60/431,335 filed Dec. 5, 2002, both hereby incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to mechanisms for securing doors from being opened by small children, and in particular, to a device suitable for doors with lever-type door handles. 
   Architectural doors may have a latch mechanism holding the door closed and operated by means of a doorknob. Particularly for interior doors, the latch mechanism may be without a lock, and therefore readily opened by anyone turning the doorknob. 
   Parents with small children who wish to secure a door, for example, a door leading to stairs or other hazards, may make use of an add-on “safety lock” that prevents the child from opening the door. A commonly available safety lock for standard doorknobs covers the doorknob with a loosely fitting shell which rotates freely around the doorknob. A child grasping the shell can turn only the shell and not the contained knob. An adult with greater hand strength may compress the shell against the doorknob so as to enable rotation of the doorknob through the shell. This type of safety lock differentiates between adults and children in part by hand strength and requires that the doorknob be rotationally symmetric. 
   In recent years, such symmetric doorknobs have given way to lever handles which can be easier for the infirm and handicapped to actuate. A safety lock using a rotating shell design does not work with such lever handle systems, which are not rotationally symmetric, and have a wide variety of lever sizes. 
   Nevertheless, it is often desired to secure doors having such lever handles from opening by small children, and in fact, lever handles may in some cases be easier for small children to open, to the extent that the child may be drawn to reach up and hang upon the lever. 
   SUMMARY OF THE INVENTION 
   The present invention provides a safety lock for lever-type door handles that blocks rotation of the handle by bracing the handle against both the handle shaft and at least one stationary point on the door structure, typically the door jam. In this way, the lever need not be fully shrouded and a wide variety of different door handles may be accommodated. 
   Specifically, the present invention provides a child safety lock for doors with lever handles of a type having a rotatable shaft extending from the door and a lever extending radially from the handle shaft. The child safety lock comprises a lever grip engaging a portion of the lever and a fulcrum element attached to the lever grip to be positioned proximate to the shaft as a fulcrum. At least one arm having a first end attached to the fulcrum element extends radially therefrom to a second end sized to interfit with a stationary door structure. As configured, a force of rotation of the lever in an unlocking direction may be conducted by the lever grip through the fulcrum element to the shaft, and through the arm to the stationary door structure. 
   Thus it is one object of the invention to provide an add-on safety lock for lever door handles. 
   The arm may be sized so that the second end interfits with a door jam adjacent to the door handle when the door is closed. 
   Thus it is another object of the invention to engage a structure commonly available near the handle. 
   The fulcrum element may be a collar surrounding the shaft. 
   Thus it is another object of the invention to provide a mechanism that is retained when locked and unlocked. 
   The collar may include at least a first and second collar portion separable for insertion of the shaft within the collar. 
   Thus it is another object of the invention to provide a collar that may conform closely to the shaft of the handle without creating problems installing it over the lever. 
   The collar may include at least one latch for releasably retaining the collar in a closed position around the shaft after the shaft is inserted into the collar. 
   It is thus an object of the invention to prevent accidental dislodgment of the collar from the shaft. 
   The collar may include space-filling elements allowing the inner opening of the collar to conform to shafts of different diameters. 
   It is thus another object of the invention to accommodate multiple handle designs with different-sized shaft or shafts that are not cylindrical. 
   The space filling elements may be spring fingers extending inward from an inner edge of the collar to flexibly press against the outer circumference of the shaft. 
   It is thus an object of the invention to provide an embodiment in which multiple spacer elements need not be provided, but which may conform and automatically adjust to the shaft size. 
   The arm may include a release allowing it to be displaced from interfitting with the stationary door structure for rotation of the lever. 
   It is thus another object of the invention to allow an adult operating the release to open the door without detaching the safety lock from the handle. 
   The arm may include a pivot operating about an axis substantially parallel to the axis of the shaft and the release may be a catch preventing pivoting of the arm except when the catch is released. 
   It is thus another object of the invention to provide a release mechanism that is simple and does not produce unwieldy extensions from the door. 
   The lever grip may be a collar surrounding the lever. 
   It is thus another object of the invention to provide a positive retention of the lever and a gripping of levers of arbitrary length in a single device. 
   The safety lock may include a second arm extending radially from the fulcrum to a second end sized to interfit with a stationary door structure. 
   It is thus another object of the invention to provide a lock that may block two directions of rotation of the lever handle. 
   The lever grip fulcrum element and arm may be polymer materials. 
   Thus it is another object of the invention to provide a device that is simple to manufacture but that reduces risk of damaging or marring the door when in direct contact with the door. 
   The release mechanism may be oriented on top of the safety lock when the safety lock is in place and locked on a door handle. 
   Thus it is another object of the invention to displace the release mechanism from the access by or sight of small children. 
   The arms may have feet portions that ride against the front surface of the door. 
   It is another object of the invention to provide a lock that rests stably on the door when attached to the door handle. 
   These particular objects and advantages may apply to only some embodiments falling within the claims, and thus do not define the scope of the invention. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  is a an exploded perspective view of the three components of the safety lock of a preferred embodiment of the invention partially assembled around a lever door handle shown in phantom; 
       FIG. 2  is a fragmentary cross-sectional, front elevational view through the assembled invention along lines  2 - 2  of  FIG. 1  showing attachment of two collar portions about the shaft of the handle and the compression of space filling elements therein; 
       FIG. 3  is a right side, elevational view of a lever grip attached to one of the collar portions for receiving the lever in a cage to retain the lever, the figure further showing the offset of the cage with respect to the collar; 
       FIG. 4   a  is a fragmentary right side, elevational view of a collar tab for holding the collar portions together; 
       FIG. 4   b  is a cross-sectional view through the collar tab along lines  4   b - 4   b  showing a stop blocking the disengagement of barbed fingers; 
       FIG. 5  is a front elevational view of the assembled components of  FIG. 1  showing blocking of the handle of a door against clockwise rotation by a first arm abutting a door jam; 
       FIG. 6  is a cross sectional view along lines  6 - 6  of  FIG. 1  showing a release allowing a folding back of a second arm of  FIG. 7 ; and 
       FIG. 7  is a fragmentary view similar to that of  FIG. 5  showing a folding back of a second arm allowing lifting of the lever. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to  FIG. 1 , a lever-type door handle  10  includes an escutcheon plate  12  fitting against a front surface of the door  14 . A shaft  16  may extend from the door  14  along a shaft axis  18  about which the shaft  16  may turn. A lever  20  extends radially from the exposed end of the shaft  16  to be grasped by the user to rotate the shaft  16  to operate a latch mechanism within the door (not shown) as is generally understood in the art. 
   Referring also to  FIG. 2 , a safety lock  22  per the present invention provides a first collar portion  24  having a hemicylindrical opening  26  for fitting about a left side of the shaft  16  as depicted and a second collar portion  28  having a hemicylindrical opening  30  for fitting about a right side of the shaft  16 , together providing a cylindrical bore through which shaft  16  may pass. 
   As seen in both  FIGS. 1 and 2 , space filling elements  36  may extend inward from the inner surfaces of the hemicylindrical cavities of first collar portion  24  and second collar portion  28 ; the space filling elements  36  being flexible fingers diverging from a line of diameter of the formed cylindrical bore in a V-form opening toward the center of the cylindrical bore. The fingers may flex outward to fill the space between the outer circumference of the shaft  16  and the inner surface of the formed cylindrical bore preventing looseness in the interfitting of the first collar portion  24  and second collar portion  28  about the shaft  16  such as would cause a rattling or inadvertent pivoting thereabout. 
   Referring now to  FIGS. 1 ,  3 ,  4   a , and  4   b , the second collar portion  28  may be held to first collar portion  24  by barbed fingers  32  extending horizontally from the first collar portion  24  and passing through retaining slots  48  on collar tabs  34  on second collar portion  28 . The barbed fingers  32  may flex inward to allow their outwardly extending barbs  50  to pass through the slots  48  in the collar tabs  34  and engage the outer surface thereof. Further engaging motion of the barbed fingers  32  and collar tabs  34  is stopped by molded stop  52  projecting upward from first collar portion  24  between the barbed fingers  32 . 
   Outward flexure of the barbed fingers  32  is sufficient to hold collar tabs  34  of second collar portion  28  in place, however, additional security is provided by means of stop plates  56  attached by living hinges  58  to an outer edge of the collar tabs  34 . The stop plates  56  fit between tips of the barbed fingers  32  after they have passed through the collar tabs  34  preventing them from flexing inward such as might disengage their barbs  50  from the surface of the collar tabs. A T-retainer  59  extends outward from the collar tabs  34  to be received in a dual width slot  60  in the stop plate  56 . One portion of the dual width slot  60  allows free passage of the head of the T-retainer  59  through the dual width slot  60  while the other portion of the dual width slot  60  is sufficiently narrow to block passage of the head of the T-retainer  59  thereby capturing the stop plate  56  beneath the head of the T-retainer  59 . A handle  62  projects outward from the stop plate  56  to allow engagement and disengagement of the stop plate  56  from the T-retainer  59 . 
   As described, the first collar portion  24  and second collar portion  28  may be thus easily assembled and disassembled about the shaft  16  without needing to thread the collar so formed over lever  20 . 
   Referring to FIGS.  1 , 2 , and  3 , the second collar portion  28  includes a cage  40  defining an opening  42  through which the lever  20  may pass to be surrounded on all sides. This opening  42  may also have space filling elements (not shown) allowing the cage  40  to conform to handle levers  20  of different widths and thicknesses or a single opening size may be used, as shown, allowing some limited and acceptable handle rotation. 
   As shown in  FIG. 3 , generally the opening  42  of the cage  40  is offset outward from the door  14  with respect to the second collar portion  28  around the shaft  16 . This offset is reversed for the lever on the opposite side of the door and yet both lever directions may be accommodated by a 180-degree rotation  46  of the second collar portion  28  about a radial axis  44 , prior to its engagement with first collar portion  24  as shown in  FIG. 1 . The barbed fingers  32  of the first collar portion  24  and the slots  48  of the collar tabs  34  of the second collar portion  28  are symmetric so as to allow this rotation  46  while still permitting the connection between the barbed fingers  32  and the slots  48 . In this way, lever handles on either side of the door  14  may be secured with the present device. 
   Referring now to  FIGS. 1 and 5 , attached to the first collar portion  24  are an upper arm  68  and lower arm  64 , each extending radially from the shaft  16  at approximately equal angular spacing about axis  18  to each other as to the lever  20 . The arm  64  is sized so that downward motion (clockwise) of the lever  20 , acting through the cage  40  against a fulcrum provided by the first and/or second collar portions  24  and  28 , brings the distal end of arm  64  upward into abutment with the vertical jam wall  66  being part of the casing of door structure. Conversely, upward motion (counterclockwise) of the lever  20  acting through the cage  40  against a fulcrum provided by the first and/or second collar portions  24  and  28  brings the distal end of arm  68  downward against the vertical jam wall  66 . 
   The arms  64  and  68  are sized so that the free rotation of the lever  20  is insufficient to cause the lock mechanism with the door  14  to withdraw the bolt (not shown) holding the door shut. The arms  64  and  68  include at their distal ends, spreaders  67  extending axially that provide an edge that may ride along the face of the door  14  to stabilize the safety lock and ensure engagement with the jam. 
   It will be understood that arms  64  and  68  together prevent the opening of the door  14  by moving the lever  20  up or down. This is the highest level of security. The arm  64  alone may, however, prevent the opening of the closed door  14  where the expectation is that the child will only be able to pull downward on the lever  20 . In this case, a parent or guardian may simply raise the lever  20  to open the door  14 . 
   An opening of the door  14  or this lower level of security may be obtained by a retraction of lever arm  68  through the use of a release lever  70 . Referring to  FIGS. 1 ,  7 , and  6 , this retraction of arm  68  is accomplished by attaching arm  68  to first collar portion  24  by means of pivot pins  72  extending axially from the first collar portion and fitting within corresponding pivot holes  74  in the proximal end of arm  68  so that arm  68  may swing about an axis generally parallel to axis  18  while remaining adjacent to the plane of the door  14 . Unintended retraction of the arm  68  when the lever  20  is to be locked against upward motion is provided by means of a flexible hook  76  extending within the arm  68  from its distal to proximal end. The hook engaging a catch surface  78  attached to the first collar portion  24  between the pivot pins  72  to which the arm  68  is attached. The hook  76 , when engaged, resists upward motion  80  of the arm  68  until the hook  76  is disengaged from the catch surface  78  by a backward pressing of the release lever  70  as indicated by arrow  82 . 
   The above-described design is amenable to injection molding where each of the arm  68 , the first collar portion  24  and the second collar portion  28  are separately molded as integral parts and assembled, the first collar portion  24  and second collar portion  28  assembled together via the barbed fingers  32  as described above, and the arm  68  assembled to the first collar portion  24  by snapping it onto the pivot pins  72 . Fabricating the safety lock of the present invention from plastic material such as polypropylene provides for good resilience and low risk of marring the door  14  and the flexibility required of the space filling elements  36 , living hinge  58 , and flexible latch hook  76 . 
   While what has been described is a preferred embodiment, it will be recognized that the principle described herein may be applicable to safety locks which engage stationary door structure not limited to the casing surrounding the door but including, for example, the slot between the door and the casing as gripped by a pin or blade extending into the slot from the distal ends of one or both of arms  64  and  68 . 
   From the description herein, variations of this invention will be understood to include those which engage portions of the surface of the door  14  with frictional elements and semi-permanent attachments to the front surface of the door. Although a collar that fully surrounds the shaft  16  is described, it will be understood that during normal use only portions of the collar contact the shaft  16 , and therefore a collar which does not fully enclose shaft  16  may be used. 
   It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.