Patent Publication Number: US-7216400-B2

Title: Door hold and release mechanism

Description:
This application claims the benefit of Provisional Application No. 60/387,790 filed Jun. 11, 2002. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates a new and improved door hold and release mechanism for use with conventional reciprocating pneumatic operated door checks or closers known in the art. 
   2. Description of the Prior Art 
   Door-checks or closers, as they are often referred to, such as the reciprocating pneumatic cylinder type used on storm, screen and similar type doors, automatically close the door after the door has been opened and then released. The door must be hand or mechanically held open while passing through or invariably the door will automatically return, possibly causing injury to the person passing through the doorway. 
   In order to hold a door open, while passing through a door equipped with the typical reciprocal door-check used on a majority of storm and screen door installations, it is necessary to first slide a “lock tab”, located on the door-check&#39;s piston rod, toward and into contact with the face of the door-check cylinder. This requires holding the door in an open position with one hand while sliding the lock-tab with the other, and then reversing the procedure to allow the door to close under action of the cylinder. 
   This two-fold operation is both clumsy and time consuming. Additionally, since sliding the lock-tab can only be done from inside the door, the prior art is only useful under circumstances where a person is leaving and then immediately returning through the door. Moreover, a dangerous scenario posed by the sliding lock-tab is that because of its operational difficulty, a person might decide not to use its hold-open function and proceed to pass through the door while the door is automatically returning to its closed position, resulting in injury. Further, in those cases where the door checks are installed on the lower portion of a door requiring bending down to operate the lock-tab, the operator is in a more precarious position for injury should the door check malfunction. 
   It is therefore a primary object of the invention to provide a door hold and release mechanism which is able to hold a door open, hands free, until the person opening the door has completely passed through the door and then subsequently release the hold on the door and allow it to close safely. 
   Another object of the invention is to provide a door hold and release mechanism which can restrain a door in an open position by the simple action of depressing a button, either by hand or foot, and releasing the restraint by a simple outward pressure on the door. 
   Still another object of the invention is to provide a door hold and release mechanism which is small and easily mounted onto a door check cylinder, which has a minimum number of moving parts and which is easily manufactured. 
   Yet another object of the invention is to provide a door hold and release mechanism which is adaptable to most, if not all, reciprocal pneumatic door-checks or closers of the type often used on conventional screen and storm doors. 
   SUMMARY OF THE INVENTION 
   According to the invention, there is provided an improved door hold and release mechanism for use with a door-check or closer of the type including a pneumatic cylinder and a reciprocating piston rod. The door hold and release mechanism of the invention includes a housing mounted onto the side wall of the pneumatic cylinder and a drop stop fitted over the piston rod close to one end of the cylinder. The piston rod passes through a hole in the drop stop which is of such size as to allow movement of the piston rod through the hole in a first position when the drop stop is substantially perpendicular to the piston rod but which restricts movement of the piston rod by friction in a second position when the drop stop is tilted at an angle other than perpendicular to the piston rod. 
   A cap button is mounted on top of the housing and is used to activate the door hold and release mechanism by depressing the button using a person&#39;s hand or foot, for example. An elongated shaft is disposed in the housing and is connected at one end to the cap button. A spring mounted inside the housing exerts a bias pressure on the shaft which opposes the external force applied to the shaft when cap button is depressed. 
   A draw bar is also mounted within the housing and has a forward end extending outwardly through the housing which is connected to the drop stop. A cam action linkage connects the other rearward end of the draw bar to the opposite end of the shaft. The linkage comprises an elongated cam slot formed within the opposite end of the shaft and a pin, which extends through both the slot and the rearward end of the draw bar. The slot is inclined at an angle with respect to the draw bar such that the draw bar is forced to move both laterally along with the shaft and in a rearward direction in response to the external forces applied to the shaft when the cap button is depressed. This in turn causes the drop stop to tilt from its first position perpendicular to the piston rod to its second position engaging the piston rod and holding the door open for passage of the operator. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
       FIG. 1  is a perspective view of a door hold and release mechanism of the invention shown mounted onto the pneumatic operated cylinder of a conventional door-check or closer; 
       FIG. 2  is an exploded view of the door hold and release mechanism and pneumatic operated door check shown in  FIG. 1 ; and 
       FIG. 3  is a cross-sectional view of the door hold and release mechanism shown in FIGS.  2 . 
   

   DESCRIPTION OF A PREFERRED EMBODIMENT 
   Referring now to the drawings and particularly to  FIGS. 1 and 2 , there is shown a door hold and release mechanism embodying the invention. As shown, the mechanism includes a housing  10  of a generally rectangular shape attached to the pneumatic cylinder  12  of a conventional door check using a mounting sleeve  11 . The sleeve  11  is of such size as to fit easily around the side walls of the cylinder  12  and is split and formed with a pair of opposed fastening tabs  13 . The tabs  13  allow the sleeve  11  to be tightened securely around the cylinder  12  using a bolt  16  an a nut  14 . This arrangement permits the housing  10  to be mounted to a variety pneumatic cylinders  12  having varying diameters as may be produced by different manufacturers. It is of course possible to dispense with the sleeve  10   a  altogether and secure the housing  10  directly to the pneumatic cylinder  12 , thus utilizing the mechanism as an integral part of a door check design. 
   Although the door hold and release mechanism of the invention is shown in the drawings as being mounted in a vertical position on top of the pneumatic cylinder  12 , it will be understood that the mechanism may be mounted as well horizontally to one side of the cylinder, this arrangement being preferred in those cases where the mechanism is secured to the door mid-way between its top and bottom ends. In this particular arrangement, the mechanism can be more easily activated by the person&#39;s hand, arm or elbow when carrying a child or groceries, for example, as opposed to using a foot when the mechanism is mounted at the bottom of the door. 
   The door hold and release mechanism of the invention further includes a rectangular cap button  18  which loosely fits over the top open end of the housing  10 . The door holding action is initiated by depressing the cap button  18  by hand or foot, for example, thereby compressing a tension spring  20  and forcing an elongated shaft  22  vertically downward through an opening in a shaft guide plate  24 . The upper end of the shaft  22  is connected to the cap button  18  by a set screw  26  which passes through the button and is loosely secured to its underneath side by a cap retainer clip  28 . The clip  28  allows the set screw  26  to turn independently of the cap button  18 . The set screw  26  threads into the upper open end  30  of the shaft  22  and, by turning, varies the tension of the tension spring  20  positioned between the guide plate  24  and the cap button  18 . 
   As shown in  FIGS. 2 and 3 , a cam action linkage assembly is provided for connecting the shaft  22  to a horizontal draw bar  34  within the housing  10 . The shaft  22  is formed at its lower end with a narrow flat section  33  which fits loosely inside a narrow opening  35  formed within the rearward end of the draw bar  34 . A linkage pin  32  passes through the opening  35  and engages a cam slot  36  formed within the flat section  33 . The cam slot  36  extends upwardly and rearwardly at an angle of about 45 degrees, for example, with respect to the longitudinal axis of the shaft  22 . As the shaft  22  moves laterally downward upon depression of the cap  18  button, the pin  32  rides to the upper end of the slot  36 , drawing the bar  34  in a rearward direction. As the shaft  22  continues to descend, it draws the bar  34  also in a downward direction locking the door in the open position, whereupon it partially returns to its starting location. A snap stop  38  is provided for limiting outward movement of the draw bar  34  as shall be more clearly described hereinafter. 
   The forward end of the draw bar  34  has a threaded opening  40  and extends outwardly through an exit hole  44  in the side wall of the housing  10 . A drop stop  46  is slidably mounted onto the reciprocating piston rod  42  of the pneumatic cylinder  12 . The drop stop  46  is secured to the forward end of the draw bar  34  by a bolt  50  and washer  56 , the bolt passing through a hole  48  in the drop stop  46  and engaging the threaded opening  40  on the draw bar  34 . 
   The piston rod  42  extends through a hole  52  in the lower end of the drop stop  46 . The hole  52  is drilled slightly larger than the diameter of the piston rod  42  and is so designed as to slip over the end of the piston rod  42  when detached from its mounting hardware. The drop stop  46  extends from just above draw bar  34  to a point substantially even with the bottom edge or rim of the pneumatic cylinder  12  as best shown in FIG.  1 . The lower end of the drop stop  46  is shaped to have a bend  54  of approximately 30 degrees from the vertical toward the bottom edge of the cylinder  12 , beginning from a point just below the hole  52  for the piston rod  42 . 
   When the door hold and release mechanism is in an inactive position as shown by the full lines in  FIG. 3 , the tension spring  20  forces the cap button  18  and attached shaft  22  to their uppermost positions at the top of the housing  10 . The pin  32  rests in the lower end of the cam slot  36 , which also is at its uppermost position, and the snap stop  38  is placed in contact with the interior wall of the housing  10 , preventing any forward motion of the draw bar  34  beyond the exit hole  44 . In this position, the drop stop  46  is perpendicular to the piston rod  42  and is free to slide along its length. 
   To hold the door open, the cap button  18  is momentarily depressed forcing the shaft  22  vertically downward guided by the shaft guide  24 . The cam slot  36  is slanted forward and exerts a rearward and downward pressure on the pin  32 , drawing both the draw bar  34  and drop stop  46  into a rearward slanting position as shown by the phantom lines in FIG.  3 . This action exerts a friction force between the hole  52  on the drop stop and the piston rod  42 . The friction force is significantly increased by the action of the cylinder  12  applying pressure against the angled tip of the drop stop bend  54 . The combined pressures hold the door in the open position. 
   The cap button  18  when released, partially returns to its starting position by the expansion of the tension spring  20  and the free travel distance in the cam slot  36 . The remaining tension on the tension spring  20  is adjusted so as not to allow a release of the door unless the weight of the door is removed from the pneumatic cylinder  12 . An outward motion of the door subsequently releases this tension and the friction hold of the drop stop  46  on the piston rod  42 . The tension spring  20  fully expands and returns the cap button  18  and all connecting parts to their starting positions. 
   When the door is held in the open position, the set screw  26  is adjusted to a point slightly less than required for a full release of the door from the friction hold by the hole  52  on the drop stop  46 . The tension on the tension spring  20  is variable and is dependent on several factors, namely, the weight of the door, the return capacity of the door-closer and the wear on both the hole  52  and the piston rod  42 . 
   The door hold and release mechanism of the invention is effortlessly operated, eliminating many of the problems inherent with the prior art. When a person passing through a door is carrying packages, or perhaps an infant, and the sudden closing of the door might otherwise cause serious harm, one simply has to hold open the door with one hand and depress the cap button  18  with the foot, or if the hold and release mechanism is mounted near the center of the door, with the forearm or elbow and then pass through the door. Upon leaving the person only has to pull or nudge the door outward with the hand, knee or shoulder and the door will very conveniently close behind him. If necessary, the door can be left in the open position when repeated trips through the doorway must be made and later closed by applying an outward pressure on the door. 
   The simple hold and release actions of a door closer equipped with the instant mechanism are far superior and less complicated than operation of the prior art devices. The use of lock-tabs supplied with prior door checks is inconvenient and requires the tab to be hand located on the piston rod to hold the door open and relocated to its former position behind a crimped portion on the piston rod to allow the door to fully close. This requires a person to hold the door open with one hand and to manipulate the tab with the other hand. 
   Although the door hold and release mechanism of the invention has been described herein mainly as an add-on feature to new or installed door checks, it is of course entirely possible to employ the device as an integral part of a door check&#39;s original design and manufacture.