Patent Publication Number: US-2010127518-A1

Title: Electric strike

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a structure of an electric strike and more particularly, to a structure of an electric strike in which a set mode of the electric strike can be conveniently adjusted from the outside of the electric strike, such that the electric strike is either in a locked or unlocked state when the power is off. 
     2. Description of the Prior Art 
     An electric strike is commonly used to control the ingress and egress to buildings. The electric strike is provided with an electromagnetic actuating device that can convert electricity to mechanical force. In general, the electromagnetic actuating device is either an electrically driven motor or a solenoid device. With the power on or off, the driving device enables the latch of a door to be lock or unlock. 
     Generally, an electric strike has two modes. One mode is called “fail-secure,” where the electric strike is not powered on and a “locked” state is presented. When the electric strike is powered on through an externally connected control system such as a card machine or a card reader, an internal actuating device is activated to unlock the latch. The second mode is called “fail-safe,” where the electric strike is continuously powered on and in a normal locked situation. When the electric strike is powered off, the internal actuating device is activated to achieve an “unlocked” state. Some electric strikes only have one of the above modes, and no selection can be made. However, the electric strike described in this present invention may be selected to set to either of the two modes above when it is installed or by operations after installed by an operator. 
     In the prior art, such as U.S. Pat. No. 6,299,225, an electric strike with the structure shown as  FIG. 1A  and  FIG. 1B  is disclosed. Its “mode select” function is achieved by the main elements which include a housing  60 , a lever  61 , a solenoid device  62  fixed to a mount  621  comprising a plunger  622  slideable in the solenoid and a block  623  fixed to one end of the plunger  622 . In the mount  621  are provided a plurality of bottom screw holes  624 , which are distributed at the front end and the back end of the mount respectively. The housing  60  is provided with a correspondingly disposed elongated slot  65  and two screw holes  66  in tandem. An adjustment screw  67  is used to pass through the elongated slot  65  of the housing  60  and is locked into one of the screw holes  624  in the mount  621  close to the block  623 . A tie screw  68  is used to pass through one of the screw holes  66  in the housing  60  and is locked into one of the screw holes  624  in the mount away from the block  623 . In practical operations, as an operator selects to lock the tie screw  68  into the screw hole  66  close to the right side or the center of the housing  60 , so that until the power is on or off, the solenoid device can drive the block  623  to a position in which it resists against the lever  61  to prevent it from rotating to unlock the door, thereby the effect of the door security mode selection is achieved. However, the structure described above is complicated. If desired, to switch between the different modes, the operator has to loosen the adjustment screw  67  followed by the tie screw  68 , push the adjustment screw  67  by toggling with an external force to enable the mount  621  and the solenoid device to translate a distance, then lock the tie screw  68  into another tie screw hole. The operation procedure above is considerably complicated. 
     Another U.S. Pat. No. 6,874,830 disclosed an improved structure. As shown in  FIGS. 2A ,  2 B and  2 C, the structure is provided with an actuating device, which also is a solenoid  72 . Similarly, a plunger of the solenoid  72  is attached with a blocking element  74  and a keeper  71 . The blocking element  74  has two projections. The keeper  71  also has two projections. When the two projections of the blocking element  74  are just moved to a position in which they are opposite to the two projections of the keeper  71 , the operation of the keeper  71  is blocked and the door therefore cannot be opened. The solenoid is fixed to a holder  73 , which is equivalent to the mount  621  described above. The main difference between the structure of U.S. Pat. No. 6,874,830 and U.S. Pat. No. 6,299,225 is that the former patent employed an eccentric wheel device as a two-position mode selector  76 . The eccentric wheel device  76  is joined with a disk  763  at its both sides by two eccentrically disposed posts  761 ,  762 . The post  761  is exposed to the outside of a housing  70 , and has a tool notch thereon by which the post  761  can be rotated by a screw driver. The post  762  is embedded into a slot in the holder  73 . If desired to switch a mode, the holder  73  carrying the solenoid  72  and the blocking element  74  may be pushed indirectly to slide in the housing  70  simply by using a screw driver to rotate the eccentric device  76  from outside. As such, the two projections of the blocking element  74  are aligned or staggered with the two projections of the keeper  71 , such that the selection of either a fail-secure or a fail-safe mode is achieved. Although this eliminates the annoyance of the necessity of removing the outer cover at the time of mode setting, such an eccentric wheel device is operative to convert a rotational torque into a linear movement. If the structure is not properly designed to constrain the solenoid and the blocking element to move in a linear direction, a part resisted against by the eccentric wheel may deflect upwards or downwards from the friction, thereby leading to instability. Furthermore, the construction of such a device is complicated, and the manufacturing and assembling of its parts is not cost effective. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide an electric strike structure of which the door security mode is changeable, and more particularly to an electric strike structure of which the door security mode can be changed easily by an ordinary operator from outside. 
     Another objective of the present invention is to provide an electric strike structure of which the door security mode is changeable and requires no complex machining. 
     Furthermore, another objective of the present invention is to provide an electric strike structure of which the door security mode is easily adjustable and accessible, cost-effective in assembly and can be stably operated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  and  FIG. 1B  are a structural exploded view and an assembly view of a structure in the prior art respectively. 
         FIG. 2A-2C  are a structural exploded view, an internal mode selection device, and an eccentric wheel device used for mode selection in the prior art respectively. 
         FIG. 3  is an exploded view of the structure of a first embodiment according to the present invention. 
         FIG. 4  is an exploded view of the structure of the actuating device of the present invention. 
         FIG. 5  is a sectional assembly view of the first embodiment according to the present invention. 
         FIG. 6  is a perspective view of the first embodiment according to the present invention. 
         FIG. 7A  is a front view of the first embodiment according to the present invention with a bottom cover removed, in which the mode is set to “fail-safe.” 
         FIG. 7B  is a sectional view of the first embodiment according to the present invention taken along the line  7 B- 7 B in  FIG. 7A . 
         FIG. 7C  shows the locked state upon powering on of the first embodiment according to the present invention after set to the “fail-safe” mode. 
         FIG. 7D  is a sectional view of the first embodiment according to the present invention taken along the line  7 D- 7 D in  FIG. 7C . 
         FIG. 8A  is a front view of the first embodiment according to the present invention with the bottom cover removed, in which the mode is set to “fail-secure.” 
         FIG. 8B  is a sectional view of the first embodiment according to the present invention taken along the line  8 B- 8 B in  FIG. 8A . 
         FIG. 8C  shows the unlocked state upon powering on of the first embodiment according to the present invention after set to the “fail-secure” mode. 
         FIG. 8D  is a sectional view of the first embodiment according to the present invention taken along the line  8 D- 8 D in  FIG. 8C . 
         FIG. 9  is an exploded view of the structure of a second embodiment according to the present invention. 
         FIG. 10  is an exploded view of an adjustment device used in the second embodiment according to the present invention. 
         FIG. 11A  is a front view of the second embodiment according to the present invention after assembling with the bottom cover removed, in which the mode is set to “fail-safe.” 
         FIG. 11B  is a sectional view of the second embodiment according to the present invention taken along the line  11 B- 11 B in  FIG. 11A . 
         FIG. 11C  shows the locked state upon powering on of the second embodiment according to the present invention after set to the “fail-safe” mode. 
         FIG. 11D  is a sectional view of the second embodiment according to the present invention taken along the line  11 D- 11 D in  FIG. 11C . 
         FIG. 12A  is a front view of the second embodiment according to the present invention after assembling with the bottom cover removed, in which the mode is set to “fail-secure”. 
         FIG. 12B  is a sectional view of the second embodiment according to the present invention taken along the line  12 B- 12 B in  FIG. 12A . 
         FIG. 12C  shows the unlocked state upon powering on of the second embodiment according to the present invention after set to the “fail-secure” mode. 
         FIG. 12D  is a sectional view of the second embodiment according to the present invention taken along the line  12 D- 12 D in  FIG. 12C . 
     
    
    
     DETAILED DESCRIPTION 
     The preferred embodiments of the present invention are illustrated in the following description in conjunction with accompany drawings, in which the reference numerals are used to represent corresponding elements. 
       FIG. 3  is an exploded view of the structure of an electric strike according to a first embodiment of the present invention. Referring to  FIG. 3 , the electric strike includes a base  10 , a shell  20 , a lever  30 , and an electromagnetic actuating device  40 . The base  10  and the shell  20  are fixed to an opposite position with respect to each other to form a housing, in which a space is formed to accommodate the lever  30  and enable it to rotate a particular angle or telescope a distance. The space may be formed by a chamber formed in the base  10  and a recess  24  formed in the shell  20 , and at least enables a locking plate  34  of the lever  30  to protrude from the base  10  to face a surface of a corresponding lock mouth in the doorframe or door panel when the electric strike is in a locked state. As such, the locking plate  34  may be engaged with the corresponding lock mouth in the doorframe or door panel to lock the door. The recess  24  of the shell  20  is used to accommodate the electromagnetic actuating device  40 . The recess  24  allows the actuating device  40  to move a distance therein in a linear direction. 
     In order to facilitate a stable positioning of the base  10  and the shell  20  during assembling and prevent the relative position of the base  10  and the shell  20  from shifting too much as a result of the shock due to frequent opening and closing of the door, a plurality of sawtoothed slots  12 ,  28  which can be engaged with each other are provided on the shell  20  and the base  10  respectively. The sawtoothed slots may be used to make the relative position of the base  10  and the shell  20  during assembling shift one to several teeth. The purpose is to adjust the position of the locking plate  34  of the lever protruding from the base  10 , in order to make the position correspond to the position of the corresponding lock mouth in the door panel or doorframe. 
       FIG. 4  shows that the electromagnetic actuating device has a longitudinal axis X. Referring to  FIG. 4 , the electromagnetic actuating device  40  may comprise several parts including a solenoid  42  which includes an actuating rod  45 , a second locking device which may be a block  46 , and an elastic body  48  which can be a compression spring disposed between the block  46  and the solenoid  42 . The actuating rod  45  may stretch a particular distance from the solenoid  42  due to the electromagnetic force when the solenoid  42  is powered on. The block  46  is fixed to one end of the actuating rod  45 . The solenoid  42  enables the actuating rod  45  to stretch or retract by the electromagnetic force in a powered on or powered off state, thereby causing the block  46  to reciprocate in a linear direction. As shown in  FIG. 3 , the lever  30  is provided with a first locking device, which may be a bump  32 . It penetrates through at least a portion of the space accommodating the lever  30  in the housing of the electric strike formed by the base  10  and the shell  20 , to a recess  24  on the shell  20 . Therefore, when the electromagnetic force causes the solenoid  42  to push the block  46  to move in the recess  24 , the bump  32  and the block  46  in the recess  24  may be in a position in which they are opposite to each other and able to resist against each other. In such a position, the lever  30  cannot be rotated to unlock the door. Therefore, such a position is called a “locked position.” When the block  46  and the bump  32  are staggered and do not resist against each other, the lever  30  can be rotated a certain angle or telescoped a distance in the space formed by the base  10  and the shell  20 . At that time, the locked state is released, and such a position is called an “unlocked position.” 
     As shown in  FIG. 3 , a spring  36  may be disposed between the lever  30  and the base  10  or the shell  20 , such that when the electric strike is powered off, the lever  30  may be fixed at a rotational angle or a protruded position by a spring force. Other than being in the form of a bump  32 , the first locking device may also be any mechanism that can engage with the second locking device (i.e., block  46 ) of the actuating device  40  to prevent the lever  30  from rotating or telescoping when the second locking device is moved to a locked position. 
       FIG. 3 ,  FIG. 5 , and  FIG. 7B  show a mechanism that is mainly used to set a “fail-safe” mode or a “fail-secure” mode of the electric strike. The mechanism includes an electromagnetic actuating device  40 , an adjustment device  52  penetrating one side of the shell  20  to resist against an end of the cylindrical cover of the solenoid  42  directly, and a hole  22  located in the shell  20  for the adjustment device  52  to penetrate to resist against the solenoid  42  ( FIG. 7B ). A locating stub  26  is provided in the recess  24  of the shell  20  for one end of the elastic body  48  of the electromagnetic actuating device  40  to abut against, thereby elastically biasing the solenoid  42  into a neutral position in the recess  24 . In the first embodiment as shown in  FIG. 3 ,  FIG. 5 , and  FIG. 7A-7D , the adjustment device  52  is a screw of which the length is fixed. The adjustment device  52  may be rotationally disposed on the shell  20 , and may move axially parallel to the longitudinal axis direction X of the electromagnetic actuating device  40 . A hole  22  with its axis substantially parallel to the axis X is provided in the shell  20  for the screw  52  to penetrate through, with threads formed therein to engage with the screw  52 . Where the screw  52  is not threaded into the hole  22 , or the screw  52  is threaded into the hole  22  from outside and the front edge of the screw  52  merely touch upon an end of the cylindrical cover of the solenoid  42 , the solenoid  42  is located in the neutral position as shown in  FIG. 7A  and  FIG. 7B . Such that the block  46  fixed to the front end of the actuating rod  45  is in a staggered position with respect to the bump  32  of the lever  30  (i.e., unlocked position). At that time, a “fail-safe” mode is set. Preferably, as shown in  FIG. 7B , the hole  22  is in a form of a counterbore butted with a threaded hole, and the depth of the counterbore may be set to a constant value according to the length of the screw  52  to be threaded into the hole  22 . When the solenoid  42  is in the neutral position as shown in  FIG. 7B , the head of the screw  52  is approximately flushed with the outmost edge of the counterbore of the hole  22 . 
       FIG. 7C  and  FIG. 7D  show the effect of the electric strike powered on as the “fail-safe” mode. Referring to  FIG. 7C  and  FIG. 7D , when the electric strike is powered on, an electromagnetic force causes the actuating rod  45  to push the block  46  to a position in which the block  46  is just opposite to the bump  32  of the lever  30  and resists against it (locked position) to result in the door being locked. When the electric strike is powered off, the electric strike goes back to the unlocked state as shown in  FIG. 7A  and  FIG. 7B . 
       FIG. 8A  and  FIG. 8B  show the manner of setting the first embodiment of the electric strike in the “fail-secure” mode. Referring to  FIG. 8A  and  FIG. 8B , when the electric strike is powered off, the screw  52  is threaded into the hole  22  with the head of the screw  52  in contact with the bottom of the counterbore of the hole  22 . The threaded-in distance just enables the screw  52  to push the electromagnetic actuating device  40  to the “locked position” in which the block  46  is opposite to the bump  32  of the lever  30  and resists against it. Moreover, a step surface  29  may be formed at a position in the recess  24  in close proximity to the solenoid  42 . Such that after the screw  52  is threaded into the hole  22 , a part of the end of the screw  52  resists against the step surface  29 , thereby preventing the screw  52  to be excessively threaded in. In order to locate the screw  52  at such a position tightly without loosening, a lock washer (not shown) may be disposed in the space between the exterior of the head of the screw  52  and the counterbore. If powered on at that time, the state of the electric strike may be changed to the state as shown in  FIG. 8C  and  FIG. 8D . Due to the electromagnetic force, the block  46  is moved forward to a position in which it is staggered with the bump  32  (unlocked position). Therefore, an unlocked state is achieved, and the set of the “fail-secure” mode is finished. 
       FIG. 5  is a perspective view of the assembly structure according to the first embodiment. Referring to  FIG. 5 , a bottom cover  90  is not assembled to the electric strike yet. A top cover  80  and the bottom cover  90  may be optional members, because a fixing ear  82  used for fixing to a doorframe or door panel together with a fixing hole  84  may be a structure that can be molded onto the base  10  directly. The recess  24  of the shell  20  may form a device directly to constrain the actuating device  40  to move linearly and not to disengage with the recess  24 . Therefore, the bottom cover  90  may be omitted. 
     In a second embodiment of the present invention, the adjustment device may also be a mechanism as shown in  FIG. 9  and  FIG. 10 . The adjustment device  520  includes a stick  521  and a pin  522 . On the surface of the stick  521  facing outward, there is a tool notch  523  used for operating by a hand tool from outside. The adjustment device  520  is rotationally disposed on the shell  20 , and may move axially parallel to the longitudinal axis X of the electromagnetic actuating device  40 . After penetrating through the round hole  22  in the shell  20  in the assembly process, the stick  521  fixes the pin  522  into a fixing hole  524  in the side surface of the stick  521 , such that the entire adjustment device presents an “L” shape. A flat step is provided at a place where the recess  24  of the shell  20  joins with the hole  22  as shown in  FIG. 11A , for providing a two-stage locking position for the pin  522 . When the stick  521  is moved in the direction parallel to the axis X and then rotated by a screw driver externally to rest the pin  522  at the first stage as shown in  FIG. 11A  and  FIG. 11B , the front edge of the stick  521  butts one end of the solenoid  42 , and pushes the solenoid  42  to enable the block  46  fixed to the front end of the actuating rod  45  and the bump  32  of the lever  30  to be in a staggered position (unlocked position). As such, the set of the “fail-safe” mode is complete.  FIG. 11C  and  FIG. 11D  show that when the electric strike is powered on, the block  46  and the bump  32  of the lever  30  present a butting state (locked position) and the door locked. 
     As shown in  FIG. 12A  and  FIG. 12B , when the stick  521  is moved and then rotated by a screw driver externally to enable the pin  522  to move towards the solenoid  42  and rotate about 90 degrees, thereby being rested at a second stage plane  525  as shown in  FIG. 12A , the front edge of the stick  521  pushes the cylindrical cover of the solenoid  42 . As such, the block  46  is moved to a position in which it abuts against the bump  32  of the lever  30  (locked position). At that time, the set of the “fail-secure” mode is complete.  FIG. 12C  and  FIG. 12D  show that when the electric strike is powered on, the block  46  is in a position in which it is staggered with the bump  32  of the lever  30  (unlocked position) and the door unlocked. 
     The present invention achieves a simplified part assembling and effective door security mode adjusting method. As compared to the prior art with multiple assembling many parts or mode adjustments, the present invention has novel and inventive features. 
     As described above, the variations and modifications may be made without departing the spirit of the present invention. They should be considered as falling within the coverage of description of the present invention.