Patent Publication Number: US-2018051485-A1

Title: Safety door latch

Description:
RELATED APPLICATION 
     This is a nonprovisional application that claims priority from co-pending U.S. provisional application Ser. No. 62/375,860 entitled “Safety Door Latch,” having filing date Aug. 16, 2016, which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to safety door latches. More particularly, the invention relates to a built-in child safety door latch for use in domestic dwellings. 
     BACKGROUND 
     The US Consumer Products Safety Commission (CPSC) reports that each year, children are injured by hazards in and around the home. On its website (CPSC.gov), it advocates the use of door knob covers and door locks to help prevent children from entering rooms and other areas with possible dangers. Door knob covers and door locks can help keep children away from places with hazards. The CPSC recommends that the door knob cover chosen is sturdy, and allows a door to be opened quickly by an adult in case of emergency. 
     As noted above, currently available child safety door knob products are made to cover a conventional door knob. Typically, such safety are not products are undesirable from an aesthetic viewpoint. They are typically made from plastic and their purpose is quite obvious, even to a child. 
     While child safety is paramount in a family home, most homeowners also go to great care in selecting decor that is attractive and matches throughout the home. Thus, there is a need for an attractive built in door child safety latch that provides security while maintaining an attractive appearance. The instant invention has responded to this need by providing a novel built in safety door latch. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     This summary is provided to introduce, in a simplified form, a selection of concepts that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
     A child safety door latch includes a pair of handles, each handle including a pushbutton biasing device. A latch is mechanically coupled to a latch biasing device. A master connector is mechanically coupled at a first end to the latch biasing device and at a second end to each of the pushbutton biasing devices. In a locked mode, the latch biasing device is biased such that the latch is disposed in a locking position. When an inwardly directed force applied to one of the pushbuttons, it mechanically translates to the master connector to create a release force component that operates on the master connector in a linear direction to retract the latch into an opening position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       While the novel features of the invention are set forth with particularity in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings, in which: 
         FIG. 1  schematically shows an exploded view of the components used in one example of a safety door latch. 
         FIG. 2  schematically shows preassembled subassemblies of one example of a safety door latch. 
         FIG. 3  schematically shows one example of a safety door latch has assembled into a doorframe facsimile. 
         FIG. 4  schematically shows a force diagram illustrating the operation of internal mechanisms of the safety door latch. 
         FIG. 5  schematically illustrates the operation of a safety door latch when deployed in connection with a door jamb. 
         FIG. 6  schematically illustrates positioning of one side panel of a door with the safety door latch installed. 
     
    
    
     In the drawings, identical reference numbers call out similar elements or components. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn, are not necessarily intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following disclosure describes a safety door latch. Several features of methods and systems in accordance with example embodiments are set forth and described in the figures. It will be appreciated that methods and systems in accordance with other example embodiments can include additional procedures or features different than those shown in the figures. Example embodiments are described herein with respect to a built-in child safety door latch. However, it will be understood that these examples are for the purpose of illustrating the principles, and that the invention is not so limited. 
     Definitions 
     Generally, as used herein, the following terms have the following meanings, unless the use in context dictates otherwise: 
     The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims or the specification means one or more than one, unless the context dictates otherwise. The term “about” means the stated value plus or minus the margin of error of measurement or plus or minus 10% if no method of measurement is indicated. The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or if the alternatives are mutually exclusive. The terms “comprise”, “have”, “include” and “contain” (and their variants) are open-ended linking verbs and allow the addition of other elements when used in a claim. 
     Reference throughout this specification to “one example” or “an example embodiment,” “one embodiment,” “an embodiment” or combinations and/or variations of these terms means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     “Mechanically coupled,” as used herein means physically linked through one or more linking components to another mechanical component in order to transfer forces, movement or the like. 
     An advantage of the safety door latch disclosed herein is inherent in its operation. The instant product is designed for child safety and, in one example, features a push button release on both sides of the door that a child will not be strong enough to operate. Using the instant safety door latch, a door will not open unless force is applied to release the latch while simultaneously pushing or pulling on a handle to open the door. Most interior doors open into the room in a home. The instant safety door latch requires someone to push the release button and push or pull the door open simultaneously creating a more complex situation for a child to act out. 
     Referring to  FIG. 1 , an exploded view of the components used in one example of a safety door latch is schematically shown. A child safety door latch  100  includes a pair of handles  1 , a set of pushbuttons  3 , a set of compression springs  4 , a plurality of setscrews  5 , a plurality of female threaded rods  6 , a plurality of button head cap screws  7 , a pair of inner shaft buttons  8 , a plurality of connectors  9 , a master connector  10 , a plurality of coiled spring pins  11 , a retaining ring  12 , a latch slider  13 , a latch compression spring  14 , a latch  15  and a latch sleeve  16 . Each of the handles  1  may, in one advantageous example, be made of a solid material such as nylon, plastic, metal or the like in a single integrated piece. As such, there is no need for the doorknob in this example to rotate, but rather it serves more as a handhold device. 
     Latch sleeve  16  includes an opening  18  sized to allow the latch  15  to slide in and out of the opening. The latch  15  includes a latch channel  27  sized to receive the latch compression spring  14  and the latch slider  13 . Each of the handles  1  include a first channel  20  sized to fit one of the compression springs  4 , which is in turn inserted on an outside end into one of the pushbuttons  3 . Each pushbutton  3  includes a threaded inner channel  33  for threading on to one of the compression springs  4 . Each handle  1  includes, for example, screw holes  22  to allow mounting onto a doorframe using screws  7 . Each handle  1  includes a second channel  24  sized to allow insertion of one of the inner shaft buttons  8 . Each handle  1  may comprise a standard doorknob or standard lever door opener shape, for example. 
     The components  1 - 16  are assembled together within a doorframe as follows. The latch compression spring  14  and the latch slider  13  are inserted into the latch  15 . A light coating of siliconized grease is applied to the latch slider  13  prior to installation. The retaining ring  12  is connected to secure the compression spring  14  in place with the latch slider  13 . One of the coiled spring pins  11  is pressed through the latch slider  13  with the master connector  10  in place such that the master connector  10  and latch slider  13  freely rotate. Four of the coiled spring pins  11  are pressed into four of the connectors  9  while held aligned with connecting holes of the master connector  10  and two of the inner shaft buttons  8  so as to attach all of these components together into right and left sides. The connectors and inner shaft buttons are assembled to ensure free-play between all moving joints. A light coating of low viscosity oil may advantageously be applied to moving joints. To further allow freedom of movement, a light coating of silicone may be applied to each inner shaft button  8 . 
     The pair of pushbuttons  3  are inserted into each handle first channel  20 . A pair of female threaded rods  6  are screwed onto each pair of set screws  5  using thread locker material applied to the setscrews  5 . A pair of the first compression springs  4  are opened until they can fit down over the inner shaft button  8  without substantial interference. It will be recognized by those skilled in the art having the benefit of this disclosure, that an equivalent piece of hardware can be substituted for the first compression spring  4  in order to avoid this bending step. One of the compression springs  4  is inserted into the first channel  20  of each handle  1 . 
     Referring now jointly to  FIG. 2  and  FIG. 3 , installation of component parts of one example of the door safety latch are schematically illustrated. The door safety latch may be packaged as a kit with subassemblies wherein each of the handles  1  are assembled with the first compression springs  4  in place as well as the pair of female threaded rods  6  screwed onto each pair of set screws  5  to form a pair of handle subassemblies  40 . Further, the latch  15 , latch slider  13 , retaining ring  12 , master connector  10 , plurality of connectors  9  and inner shaft buttons  8  may all be connected as a flexible latch sleeve subassembly  50 . These subassemblies may be then installed into a doorframe by assembling the flexible latch sleeve subassembly  50  into a door while sliding the latch sleeve into the doorjamb side of the door. The latch sleeve is loosely attached to the door. A handle  1  with threaded rods  6  attached as standoffs to one side of one may also be loosely attached. One of the pushbuttons  3  is screwed onto a compression spring  4  that is held within each handle  1 . In one example, hex nuts and allen keys may be used to help hold the pushbuttons in place. The opposing handle may then be slid into place and screwed to opposite handle. Screws may be kept loose until the final assembly is finished. Using setscrews or the like to fix the various components such as the pushbuttons and latch in place, the second push button  3  may then be screwed onto the compression spring  4  and tightened, as with an allen wrench. It is optional to attach one handle to the flexible latch sleeve subassembly  50  before positioning it into the doorframe  55 . Once the assemblies are in place the screws on the latch sleeve maybe tightened. The handles may be adjusted towards the edge of the door before tightening the components so that the latch is fully extended out but no springs are being pressed. The screws can then be tightened. The installation can then be tested and positioned as needed. 
     Referring now to  FIG. 4 , a force diagram illustrating the operation of internal mechanisms of the safety door latch is schematically shown. The plurality of connectors  9  are connected to the master connector  10  as described above. The master connector  10 , in turn, is connected to the latch slider  13 . The other connected components, such as the latch  15  are not shown in this drawing for the sake of simplicity and explaining the operational mechanism, however, it should be assumed that they are also attached as described above. Note that, when assembled inside a doorframe, the plurality of connectors  9  are angled inwardly to form an acute angle α with respect to the linear edges  32  of the master connector  10 . In other words, assuming a vertical line parallel to the linear edges  32 , all of the plurality of connectors  9 , when properly assembled, would be angled inwardly toward that vertical line so as to translate force F 1  or F 2  to produce a release force FR in a direction sufficient to release the latch  15 . In a locked mode, no inwardly directed force F 1  or F 2  is applied to either pushbutton. In the locked mode, all of the components are biased by the various compression springs such that the latch  15  protrudes from the latch sleeve  16 , holding the door locked. 
     When in operation, an inwardly directed force F 1  or F 2  is applied to one of the pushbuttons  3 . The applied force is mechanically translated to one of the pairs of connectors  9  thereby creating a release force component FR causing the plurality of connectors  9 , which are attached to the master connector  10 , to pull the master connector  10  in a linear direction, which in turn draws the latch slider  13  and latch  15  into the latch sleeve  16 , thereby releasing the door latch and allowing the door to be opened. 
     Referring now to  FIG. 5 , the operation of a safety door latch when deployed in connection with a door jamb is schematically illustrated. There shown in a cutaway cross-section is a doorjamb  87  having a latch notch  82  recessed therein in the usual manner. In operation, as the activation assembly is forced in a direction moving in or out of the page, the latch  15  is withdrawn from the latch notch  82 . When force is removed from either pushbutton, flexible latch sleeve subassembly  50  returns to its normal biased state and the latch  15  returns to a latched position indicated by  15 N. In this way, the latch  15  is translated in and out of latched position as designated by double arrow  36 . Thus, applying force to either pushbutton will unlatch the door and allow it to be pushed or pulled open as the case may be. 
     Referring now to  FIG. 6 , positioning of one side of a door with the safety door latch installed is schematically illustrated. Here shown handle  1  housing pushbutton  3  is mounted in a door  73 . The latch  15  is shown in a normally latched position. The handle  1  is also mounted to the door for the purpose of pulling the door open or pushing the door when the latch  15  is disengaged by pushing button  3 . Of course, if the door is hinged such that it is opened by pushing, a handle is not necessary. Those skilled in the art will also recognize that it is not necessary to shape the handle as shown in the figures, but alternative shapes such as elongated handles, levers and the like may also be used. 
     The invention has been described herein in considerable detail in order to comply with the Patent Statutes and to provide those skilled in the art with the information needed to apply the novel principles of the present invention, and to construct and use such exemplary and specialized components as are required. However, it is to be understood that the invention may be carried out by different equipment, and devices, and that various modifications, both as to the equipment details and operating procedures, may be accomplished without departing from the true spirit and scope of the present invention.