Abstract:
A door stop is attached to a wall at the same height as a doorknob. When the door is swung into an open position, the door stop is lifted. The doorknob passes under the door stop, which is then dropped so that it rests on the axel connecting the doorknob to the door. This operates to hold the door in place.

Description:
FIELD OF THE INVENTION 
   The invention relates generally to holding open a hinged door. 
   BACKGROUND OF THE INVENTION 
   Hinged doors are widely used in virtually every commercial and residential building. They are typically opened by a doorknob positioned along the side of the door opposite to the hinges. One example of is shown in FIGS. 1 and 2 of U.S. Pat. No. 5,771,533, titled “Door Stopping Device,” issued to Wang Kuang-Pin on Jan. 30, 1998, which is incorporated by reference. 
   Various methods have been used to hold these hinged doors in an open position. The mentioned patent, for example, attaches a swinging leg with a rubber foot to the bottom of the door. When this leg is swung to the upper position, it does not interfere with the normal opening and closing of the door. When the leg is swung to the lower position, it prevents the door from closing. The operation and construction of this device are further detailed in the mentioned patent and illustrated in  FIGS. 3–16 . One disadvantage of this design is that it requires the apparatus to be attached to the door. This detracts from the overall appearance of the door. And, with time and use, the stress and strain applied by the apparatus can damage the door. 
   Another common method of holding a swinging door in an open position uses a simple hook and latch mechanism. A hook is attached to the bottom corner of the door and a corresponding latch is attached to the wall. When the door is in the fully open position, the hook engages the latch to hold it open. Like the above-mentioned design, however, the addition of a hook or latch on the bottom corner of the door detracts from its overall appearance and with use can damage the door. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide a simple mechanism for holding a door open. 
   It is another object of the invention to avoid adding hardware to the door itself. 
   According to one aspect of the invention, an apparatus is provided which is especially suitable for holding a door in an open position. The door has a knob connected to the door by an axel. The apparatus has an elongated base, a first and a second arm and a yoke. The elongated base has a first and a second end. The elongated base defines at least one hole for mounting the elongated base on a wall at a height approximately equal to the knob. The first arm has an inner and an outer end. The inner end of the first arm is pivotally attached to the first end of the base. The second arm has an inner and an outer end. The inner end of the second arm is pivotally attached to the second end of the base. The yoke is connected between the outer end of the first arm and the outer end of the second arm so that the yoke can be lifted above the knob as the door moves to a fully open position and then rested on the axel connecting the knob to the door to prevent the door from closing. A cushioned door stop mounted on the elongated base between the first end and the second end. 
   According to further aspects of the invention, the elongated base is constructed from a metal strap. The first end and the second end are bent at an approximately ninety degree angle so that the first end forms a first end plate and the second end forms a second end plate. The first arm, the second arm and the yoke are constructed from a single piece of wire. The yoke has a middle portion which is bent along a semi-circle and an outer portion on each side of the middle portion which extends horizontally from the semi-circle. The radius of the semi-circle is less than a radius of the knob and greater than a radius of the axel connecting the knob to the door. 
   According to another aspect of the invention, a doorknob holder is especially suitable for holding a door in an open position. The doorknob holder includes a base and a wire frame. The base is formed from a metal strap bent at each end at an approximately ninety degree angle. Each end defines a hole. The wire frame has a yoke and a pair of parallel arms extending from each end of the yoke. An end of each of the parallel arms is bent and passes through one of the holes in the ends of the elongated base so that the wire frame is pivotally attached to the elongated base. The yoke is configured to engage a doorknob by resting on an axel behind the doorknob to prevent the door from moving to a closed position. 
   According to further aspects of the invention, the yoke has a middle portion that forms the shape of a semicircle. The semicircle has a radius that is less than a standard doorknob but greater than a standard axel connecting a doorknob to a door. 
   According to another aspect of the invention, a door is held in an open position with a yoke. The yoke is pivotally connected to a wall at a height approximately equal to a height of a doorknob attached to the door. The yoke is lifted so that the yoke is positioned slightly above the doorknob. The door is swung into an open position so that the doorknob swings past the yoke. The yoke is dropped so that the yoke rests on an axel connecting the doorknob to the door. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings and description, reference numerals are used to identify various parts. Some parts may appear in more than one drawing, and the same numeral is used to identify such parts. 
       FIG. 1  is a perspective view of a doorknob holder  100 . 
       FIG. 2  is a side view of the doorknob holder  100  engaging a doorknob to hold a door in an open position. 
       FIG. 3  is a side view of the doorknob holder  100  in a disengaged position. 
       FIG. 4A  is a front view of the doorknob holder  100 . 
       FIG. 4B  is a top view of the doorknob holder  100 . 
       FIG. 4C  is a side view of the doorknob holder  100 . 
       FIG. 5  is a perspective view of a base  502  for a doorknob holder that includes a cushioned doorknob stop  504 . 
   

   DETAILED DESCRIPTION 
   A simplified door stop operates by engaging the doorknob. It avoids the need for attaching additional hardware to the door. It can be constructed using inexpensive materials. Specifically, turning to  FIG. 1 , a doorknob holder  100  is constructed from two parts. A metal strap forms the base  102  and a wire frame  104  forms the engagement mechanism. The base  102  is approximately three to four inches long. It defines a pair of holes  103  which are used for mounting. Each end of the metal strap forming base  102  is bent at a right angle to form end plates  106  and  108 . Both of these extend approximately one half of an inch out away from the body  110 . The end plates  106  and  108  have rounded corners. The end plates  106  and  108  each define a hole  109  which is used to support the wire frame  104 . 
   The wire frame  104  is formed from a single piece of strong, metal wire. It includes a yoke  112  and two arms  114  and  116 . The yoke  112  is used to engage the doorknob. The middle portion of the yoke  112  is bent upward around a semi-circle and on either side of this semi-circle, the wire extends horizontally. The radius of this semi-circle is approximately one inch. The yoke  112  is shaped in this manner so that it will engage a doorknob. 
   As shown in  FIG. 2 , the middle portion of the yoke  112  will rest upon the shaft that connects a knob to a door. Because the radius of the curvature of the middle portion of the yoke  112  is smaller than that of a standard doorknob but greater than the radius of the shaft connecting the knob to the door, it will rest on the shaft between the knob and the door. When so positioned, it will prevent a door from closing because the doorknob is held back by the yoke  112 . 
   Returning to  FIG. 1 , on each end of yoke  112 , the wire is bent at a right angle to form arms  114  and  116 . These extend back approximately two and a half inches to accommodate a standard doorknob. The back end of arms  114  and  116  are bent and pass through the holes in end plates  106  and  108 . This forms a pivotal connection between the wire frame  104  and the base  102 . 
   Turning again to  FIG. 2 , the doorknob holder  100  is secured to a wall  202  using the holes  103  in body  110 . Screws can be used to attach the doorknob holder  100 . It is positioned at the same height as the knob  204  on door  206 . To hold the door  204  in place, the wire frame  104  is lifted to an elevated position (shown with dashed lines). When the doorknob is within the wire frame  104 , it is released so that the yoke  112  rests on the axel  208  connecting the knob  204  to the door  206 . In this position, the doorknob holder  100  prevents the door  206  from closing. To release the door, the wire frame  104  is again lifted and the door is closed moving the knob out of the holder  100 . 
   Turning to  FIG. 3 , the doorknob holder  100  is shown in a released position. Here the wire frame  104  hangs down from the base  102 . 
   Turning to  FIGS. 4A ,  4 B and  4 C, the doorknob holder  100  is shown from a front, top and side view, respectively. In  FIG. 4B , the engagement between the arms  114  and  116  and the end plates  106  and  108  are seen most clearly. Each arm  114  and  116  is bent at its end at a right angle to form a pivot portion  402  and  404  of the respective arm. The pivot portions  402  and  404  are aligned along a common axis  406 . The pivot portions  402  and  404  pass through the holes in the end plates  106  and  108 , respectively. The terminal ends  408  and  410  are then bent back again at a right angle to prevent them from slipping out of the holes. 
   Turning to  FIG. 5 , an alternative design for the base is shown. This base  502  is constructed in the same fashion as the one shown in  FIG. 1 , namely base  102 , except that it includes a cushioned knob stop  504 . The knob stop  504  is made of rubber or other pliable material. In this configuration, a single hole may pass though the knob stop  504  and base  502  for mounting. In addition, the arms of the wire frame would need to be lengthened an amount equivalent to the thickness of the knob stop  504 . 
   Although the invention has been shown and described with reference to specific embodiments, those skilled in the art will appreciate that many modifications can be made. Likewise, although approximate dimensions have been given to accommodate a standard doorknob, these can be adjusted as appropriate. All such modifications are intended to be encompassed within the scope of the following claims.