Patent Publication Number: US-2015084349-A1

Title: Fire Bolt Assembly for a Door

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a fire bolt assembly and, more particularly, to a fire bolt assembly preventing opening of a door when exposed to a fire. 
     It is known to mount a fire bolt assembly in a door for automatically locking the door in a closed state when a fire occurs, preventing flowing of smoke and fire from one side of the door into the other side to increase the time and opportunities of escape. In an approach, a fire bolt assembly includes a receiving tube mounted in a door, a positioning bolt received in the receiving tube and biased by a spring received in the receiving tube, and a stop member secured in an opening of the receiving tube for maintaining the positioning bolt in the receiving tube. The positioning bolt is moved out of the receiving tube and engages with an engaging hole in another door or a door frame when the stop member melts due to the heat of the fire, allowing locking of the door in the event of a fire. However, the spring could lose its elasticity during the fire and, thus, can not reliably push the positioning bolt to the locking position. 
     Thus, a need exists for a fire bolt assembly for a door which is capable of reliably preventing the door from being opened when exposed to a fire. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention solves this need and other problems in the field of fire bolt assemblies for reliably locking doors during fires by providing a fire bolt assembly including a receiving tube adapted to be mounted in a door. The receiving tube includes front and rear ends spaced along a first axis. The receiving tube further includes a receiving space extending along the first axis through an end face of the front end of the receiving tube. A mounting member is fixed to the front end of the receiving tube and includes an axial hole in communication with the receiving space of the receiving tube. The mounting member is adapted to be fixed on an end face of the door. A positioning bolt is received in the receiving space of the receiving tube. The positioning bolt includes front and rear ends spaced along the first axis. The positioning bolt further includes a receptacle defined in the rear end of the positioning bolt. A spring is received in the receiving space of the receiving tube. The spring biases the front end of the positioning bolt to an extended position outside of the receiving space of the receiving tube. A stick is received in the receiving space of the receiving tube and includes an abutment end. A stop member is securely mounted in the axial hole of the mounting member. The stop member is made of a material having a melting point lower than melting points of the receiving tube, the mounting member, the positioning bolt, the spring, and the stick. 
     The stop member holds the positioning bolt in a retracted position in the receiving space of the receiving tube. The abutment end is received in the receptacle of the positioning bolt when the stop member is in the retracted position. 
     The spring moves the front end of the positioning bolt out of the front end of the receiving tube when the stop member melts, and the abutment end of the stick disengages from the receptacle of the positioning bolt and moves to a blocking position preventing the positioning bolt from moving from the extended position to the retracted position. 
     In a form shown, the receptacle extends from the rear end through the front end of the positioning bolt. A pin is received in the rear end of the receiving tube and extending perpendicularly to the first axis. The spring is compressed between the rear end of the positioning bolt and the pin when the positioning bolt in the retracted position. The stick includes a pivotal end pivotably connected to the pin. The stick pivots to the blocking position after disengaging from the receptacle of the positioning bolt when the stop member melts. 
     The present invention will become clearer in light of the following detailed description of illustrative embodiments of this invention described in connection with the drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The illustrative embodiments may best be described by reference to the accompanying drawings where: 
         FIG. 1  shows a schematically perspective view of a fire bolt assembly according to the present invention and a door to which the fire bolt assembly is mounted. 
         FIG. 2  shows an exploded, perspective view of the fire bolt assembly of  FIG. 1 . 
         FIG. 3  shows a perspective view of a stop member of the fire bolt assembly of  FIG. 1 . 
         FIG. 4  shows a cross sectional view of the fire bolt assembly and the door of  FIG. 1  according to section line  4 - 4  of  FIG. 1 , with another door shown aligned with the door. 
         FIG. 4A  shows an enlarged view of a circled portion of  FIG. 4 . 
         FIG. 4B  is a cross sectional view taken along section line  4 B- 4 B of  FIG. 4 . 
         FIG. 5  shows a cross sectional view similar to  FIG. 4 , with a positioning bolt of the fire bolt assembly of  FIG. 4  moved into a coupling hole in the other door after the stop member melts. 
         FIG. 6  is a cross sectional view taken along section line  6 - 6  of  FIG. 5 . 
       All figures are drawn for ease of explanation of the basic teachings of the present invention only; the extensions of the figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiments will be explained or will be within the skill of the art after the following teachings of the present invention have been read and understood. Further, the exact dimensions and dimensional proportions to conform to specific force, weight, strength, and similar requirements will likewise be within the skill of the art after the following teachings of the present invention have been read and understood. 
       Where used in the various figures of the drawings, the same numerals designate the same or similar parts. Furthermore, when the terms “first”, “second”, “third”, “upper”, “lower”, “inner”, “outer”, “front”, “rear”, “side”, “end”, “portion”, “radial”, “vertical”, “inward”, “outward”, “spacing”, “width”, “length”, and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A fire bolt assembly is shown in the drawings and generally designated  10 . According to the form shown, fire bolt assembly  10  is mounted in a door  106 . Door  106  includes an end face  108  extending in a vertical direction and a mounting hole  110  extending along a first axis X perpendicular to the vertical direction and having an opening  111  in end face  108 . Door  106  and another door  112  are respectively and pivotably mounted to opposite sides of a door frame. Door  112  includes an end face  114  extending in the vertical direction and a coupling hole  116  formed in end face  114  and aligned with mounting hole  110  of door  106  when doors  106  and  112  are in a closed state. It can be appreciated that door  112  can be replaced with a door frame having coupling hole  116  formed in end face  114  thereof. 
     According to the form shown, fire bolt assembly  10  includes a receiving tube  117  made of metal and having circular cross sections. Receiving tube  117  includes front and rear ends  119  and  131  spaced along first axis X. Receiving tube  117  further includes a receiving space  133  extending along first axis X and having an opening  135  in front end  119 . Rear end  131  of receiving tube  117  includes two diametrically opposed pin holes  137 . A pin  139  extends through pin holes  137 . Several tabs protrude outwards from rear end  131  of receiving tube  117  along first axis X and are spaced from each other in a circumferential direction of rear end  131  of receiving tube  117 . Receiving tube  117  is received in mounting hole  110  of door  106  with front end  119  of receiving tube  117  facing end face  108  of door  106 . 
     According to the form shown, fire bolt assembly  10  further includes a mounting member  32 . Mounting member  32  includes a mounting plate  34  having rectangular cross sections and having first and second faces  36  and  38  spaced along first axis X. Four spaced fixing holes  40  are provided in mounting plate  34  and extend from first face  36  through second face  38  of mounting plate  34 . Mounting member  32  further includes a sleeve  42  protruding from second face  38  and extending away from first face  36  of mounting plate  34  along first axis X. Sleeve  42  includes a front end  43  interconnected to second face  38  of mounting plate  34  and a rear end  44  spaced from front end  43  along first axis X and distant to second face  38  of mounting plate  34 . An axial hole  46  extends from first face  36  of mounting plate  34  through sleeve  42  along first axis X and includes an opening  48  in first face  36  of mounting plate  34 . Opening  48  includes an inner periphery  50  ( FIG. 4A ) that is rounded such that the maximum inner diameter of opening  48  is larger than an inner diameter of axial hole  46 . 
     Sleeve  42  of mounting member  32  further includes inner and outer peripheries spaced in a radial direction perpendicular to first axis X. Sleeve  42  of mounting member  32  further includes first and second engaging portions  52  spaced along a second axis Y perpendicular to the first axis X. In the form shown, each engaging portion  52  is a radial hole extending in the radial direction from the outer periphery through the inner periphery of sleeve  42 . Each engaging portion  52  includes upper and lower end faces  54  and  55  spaced along a third axis Z perpendicular to first and second axes X and Y. Each engaging portion  52  further includes a coupling face  56  formed by a side wall interconnected between upper and lower end faces  54  and  55  and extending along the third axis Z. Coupling faces  56  of first and second engaging portions  52  are spaced from second face  38  of mounting plate  34  along first axis X ( FIG. 4A ). Furthermore, sleeve  42  of mounting member  32  extends through front end  119  of receiving tube  117  and is secured in receiving space  133  of receiving tube  117  by welding such that front end  119  of receiving tube  117  abuts second face  38  of mounting plate  34 . Screws  88  extend through fixing holes  40  of mounting plate  34  into door  106  to secure mounting member  32  to door  106  with first face  36  of mounting plate  34  flush with end face  108  of door  106  ( FIG. 1 ). 
     According to the form shown, fire bolt assembly  10  further includes a stop member  58  made of plastic material. Stop member  58  includes a stop plate  60  having front and rear surfaces  62  and  64  spaced along first axis X. Stop plate  60  of stop member  58  further includes a peripheral wall  65  tapering from front surface  62  towards rear surface  64  and having a conicity corresponding to inner periphery  50  of opening  48  of mounting plate  34 . Stop member  58  is mounted in axial hole  46  of mounting member  32 , with peripheral wall  65  of stop plate  60  abutting inner periphery  50  of opening  48  of mounting member  32 . 
     Stop member  58  further includes first and second legs  66  spaced along second axis Y and each protruding from rear surface  64  and extending away from front surface  62  of stop plate  60  along first axis X. Each leg  66  includes a connecting end  76  interconnected to rear surface  64  of stop plate  60  and a free end  78  spaced from connecting end  76  along first axis X and distant to rear surface  64  of stop plate  60 . Each leg  66  further includes outer and inner side faces  68  and  70  spaced along second axis Y. Inner side faces  70  of legs  66  face each other. Outer side face  68  of connecting end  76  of each leg  66  is spaced from sleeve  42  of mounting member  32 . A spacing perpendicular to first axis X between inner side faces  70  of connecting ends  76  of legs  66  is smaller than that between inner side faces  70  of free ends  78  of legs  66 . A width perpendicular to first axis X between outer side faces  68  of free ends  78  of legs  66  is larger than a diameter of axial hole  46  of mounting member  32 . Each leg  66  further includes upper and lower faces  72  and  74  spaced along third axis Z. A hook  80  is formed on outer side face  68  of each leg  66  and includes an inclined face  81  adjacent to free end  78  of each leg  66 . Hook  80  further includes an engaging face  82  facing rear surface  64  of stop plate  60  and extending along third axis Z. A projection  84  is formed on outer side face  68  of each leg  66  and adjacent to a side of hook  80 . Projection  84  of each leg  66  includes a stop face  86  extending along third axis Z. 
     In installation of stop member  58  into axial hole  46  of mounting member  32 , legs  66  of stop member  58  are extended into axial hole  46  of mounting member  32  with free ends  78  of legs  66  pressed radially inward. Free ends  78  of legs  66  deform so that inclined face  81  of each leg  66  slides along inner periphery  50  of opening  48  of mounting member  32  to guide legs  66  of stop member  58  into axial hole  46  of mounting member  32 . When hooks  80  of stop member  58  are respectively aligned with engaging portions  52  of sleeve  42  of mounting member  32 , each hook  80  of stop member  58  is engaged in one of engaging portions  52  of sleeve  42  by the resiliency of legs  66  with engaging face  82  of each hook  80  engaged with one of coupling faces  56  of engaging portions  52 , preventing movement of stop member  58  relative to mounting member  32 . Furthermore, upper and lower faces  72  and  74  of each leg  66  respectively abut upper and lower end faces  54  and  55  of each engaging portion  52 . 
     According to the form shown, a positioning bolt  151  is slideably received in receiving space  133  of receiving tube  117  and includes front and rear ends  153  and  155  spaced along first axis X. Front end  153  of positioning bolt  151  includes an abutting periphery  157  tapering away from rear end  155  of positioning bolt  151 . Positioning bolt  151  further includes a flange  159  on rear end  155 . Flange  159  has a diameter perpendicular to first axis X greater than those of positioning bolt  151  and axial hole  46  of mounting member  32 . Positioning bolt  151  further includes a receptacle  171  extending from rear end  155  through front end  153  along first axis X. Two annular grooves are formed in outer periphery of positioning bolt  151 , forming two shoulders  173  between abutting periphery  157  and flange  159 . Front end  153  of positioning bolt  151  is spaced from rear surface  64  of stop plate  60  along first axis X by a spacing T. Positioning bolt  151  is initially in a retracted position ( FIGS. 4 and 4B ). 
     According to the form shown, a stick  175  is received in receiving space  133  of receiving tube  117  and includes an abutment end  177  and a pivotal end  179 . Pin  139  extends through pivotal end  179 , allowing stick  175  to pivot about a pivot axis defined by pin  139 . 
     According to the form shown, a spring  100  is received in receiving space  133  of receiving tube  117  and mounted around stick  175  and is compressed between rear end  155  of positioning bolt  151  and pin  139 . Spring  100  includes a first end  102  abutting against rear end  155  of positioning bolt  151  and a second end  104  abutting against an outer periphery of pin  139  so that front end  153  of positioning bolt  151  is biased by spring  100  and presses against inner side faces  70  of first and second legs  66  of stop member  58 , with front end  153  of positioning bolt  151  spaced from rear surface  64  of stop plate  60  along first axis X by spacing T ( FIG. 4 ). Thus, stop member  58  is not pressed by positioning bolt  151  and, thus, will not disengage from mounting member  32 , retaining positioning bolt  151  in the retracted position in receiving space  133  of receiving tube  117 . When positioning bolt  151  and spring  100  are received in receiving space  133  of receiving tube  117 , the tabs of receiving tube  117  are bent to form the end face of rear end  131  of receiving tube  117 , retaining positioning bolt  151  and spring  100  in receiving space  133  of receiving tube  117  (see  FIGS. 2 and 4 ). 
     Fire bolt assembly  10  provides fire-resistant functions. Specifically, stop member  58  retains positioning bolt  151  in receiving tube  117  when fire bolt assembly  10  is in normal situations ( FIGS. 4 and 4B ). Note that a portion of stick  175  including abutment end  177  is in a non-blocking position received in receptacle  171  of positioning bolt  151  in the retracted position. 
     On the other hand, when doors  106  and  112  and fire bolt assembly  10  are exposed to a fire and when stop member  58  melts by the heat of the fire, front end  153  of positioning bolt  151  is biased by spring  100  and moved out of receiving tube  117  to an extended position to engage with coupling hole  116  in door  112 , locking doors  106  and  112  and preventing doors  106  and  112  from undesired opening ( FIGS. 5 and 6 ). Note that flange  159  of positioning bolt  151  abuts against rear end  44  of sleeve  42  when front end  153  of positioning bolt  151  extends out of front end  119  of receiving tube  117  while stop member  58  melts. Shoulders  173  of positioning bolt  151  are also received in coupling hole  116 . If doors  106  and  112  pivot through a small angle under action by an external force, interference occurs between one of shoulders  173  of positioning bolt  151  and a portion of an inner periphery of coupling hole  116  adjacent to end face  114 , preventing further pivotal movement of doors  106  and  112 . Thus, positioning bolt  151  will not disengage from coupling hole  116  of door  112 , avoiding opening of doors  106  and  112 . 
     Note that stick  175  is located outside of receptacle  171  of positioning bolt  151  after positioning bolt  151  reaches the extended position. Furthermore, stick  175  pivots downward under action of the gravitational force to a blocking position aligning with an end face of rear end  155  but not aligned with receptacle  171  ( FIG. 6 ). Thus, positioning bolt  151  can not move from the extended position to the retracted position. Even if spring  100  loses its elasticity by the heat of the fire, positioning bolt  151  is reliably retained in the extended position by stick  175  to reliably avoid positioning bolt  151  from disengaging from coupling hole  116  of door  112 . 
     Furthermore, fire bolt assembly  10  reduces failure of the locking function of positioning bolt  151 . Specifically, only two legs  66  of stop member  58  are received in axial hole  46  of mounting member  32  so that less material of the melted stop member  58  remains in the mounting member  32 . Thus, positioning bolt  151  will not be blocked by the melted stop member  58  and can reliably move out of receiving tube  117  after stop member  58  has melted. 
     Now that the basic teachings of the present invention have been explained, many extensions and variations will be obvious to one having ordinary skill in the art. For example, positioning bolt  151  does not have to include flange  159  in a case that the length of positioning bolt  151  along first axis X is larger than that of coupling hole  116  in door  112 . Furthermore, positioning bolt  151  does not have to include shoulders  173 . Furthermore, coupling face  56  can be in the form of a protrusion instead of a radial hole. Although second axis Y is perpendicular to the vertical direction and third axis Z is parallel to the vertical direction in the form shown, it can be appreciated that second axis Y can be parallel to the vertical direction and third axis Z can be perpendicular to the vertical direction. Receptacle  171  can be a blind hole defined in rear end  155  of positioning bolt  151 . 
     Thus since the invention disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of which forms have been indicated, the embodiments described herein are to be considered in all respects illustrative and not restrictive. The scope of the invention is to be indicated by the appended claims.