Patent Publication Number: US-9410352-B2

Title: Door closer provided with unit for adding door-closing force

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is the United States National Stage of and claims priority to International Application No. PCT/KR2013/011061, which was filed Dec. 2, 2013, that claims priority to Korean Application No. 10-2012-0139176 filed Dec. 3, 2012, titled “DOOR CLOSER PROVIDED WITH UNIT FOR ADDING DOOR-CLOSING FORCE”, both of which are incorporated herein by reference in their entirety. 
     TECHNICAL FIELD 
     The present invention relates to a door closer which automatically closes a hinged door by elastic force when the hinged door is opened. 
     BACKGROUND ART 
     A door closer is typically attached to a hinged door such as a front door, fire door, etc. of a house, apartment, officetel, etc. so as to automatically close the door by elastic force when it is opened. In a typical door closer, when the opening angle of the door increases, the expansion of a spring increases, and thus the elastic force increases. Due to the nature of this structure, when the door is almost closed as the door closer operates, the spring is restored to its original length from the state where it is fully expanded, which decreases the elastic force, and thus it is likely that the door is not completely closed. 
     In order to cope with this problem, door closers provided with a unit for adding door-closing force in a state where the door is almost closed are disclosed in prior art documents such as, for example, Japanese Patent No: 2881552, Korean Patent No: 823143, Korean Patent No: 823854, etc. However, the unit for adding door-closing force is attached to the outside of a housing of the door closer, which increases the size and weight of the door closer and the risk of failure. 
     DISCLOSURE 
     Technical Problem 
     An object of the invention is to provide a door closer which comprises a unit for adding door-closing force that is provided in a housing. 
     Moreover, another object of the invention is to provide a door closer which can be mounted to a door such that the door can be opened 180° without having to extend the length of a link even when a large spring is mounted to the inside of a housing to increase the elastic force. 
     Technical Solution 
     The present invention provides a door closer comprising: a housing which is fixed to a door; a link of which one end is connected to a door frame; a link shaft which is inserted into the housing, of which an upper end projecting to the outside of the housing is connected to the other end of the link, and which is elastically pressurized to rotate in a direction that the door is closed; and a power adding unit which adds power to close the door, the power adding unit comprises a cam which coaxially rotates with the link shaft in the housing and a cam pusher which is elastically pressurized to be in close contact with the outer circumferential surface of the cam, the outer circumferential surface of the cam comprises an arc surface portion which is spaced apart an equal distance from the rotation axis of the cam, a concave surface portion which is spaced apart a distance shorter than the arc surface portion from the rotation axis of the cam, and a pair of projection corner portions which connect the arc surface portion and the concave surface portion, and when the outer circumferential surface of the cam, with which the cam pusher comes into contact, is switched from the arc surface portion to the concave surface portion as the cam rotates, the rotation force of the link shaft is increased by the elastic pressing force of the cam pusher. 
     The door closer of the present invention may further comprise a pinion gear which coaxially rotates with the link shaft; a piston which extends in the longitudinal direction of the housing, is inserted into the housing to reciprocate in the longitudinal direction of the housing, and comprises a rack gear portion which is formed on one end thereof and engaged with the pinion gear; and a first coil spring which elastically pressurizes the piston such that the link shaft rotates in a direction that closes the door. 
     The piston may further comprise a piston base portion which is formed on the other end thereof and a piston body portion which connects the piston base portion and the rack gear portion, the first coil spring may be put on the piston body portion and may be compressed and accumulates elastic energy when the link shaft rotates in a direction that closes the door, in which one end of the first coil spring, which is relatively close to the link shaft, may be restricted to move toward the link shaft in the housing and the other end of the first coil spring, which is relatively far from the link shaft, may be pushed by the piston base portion and moves toward the link shaft such that the first coil spring is compressed. 
     A first spring hole, into which the first coil spring is inserted, a rack gear hole, through which the rack gear portion reciprocates and which has an inner diameter smaller than the inner diameter of the first spring hole and is connected to the first spring hole in a line, and a receiving groove, which has an inner diameter smaller than the inner diameter of the first spring hole and greater than the inner diameter of the rack gear hole, may be formed at the connection between the first spring hole and the rack gear hole in the housing, the door closer may further comprise a damping oil which is filled in the first spring hole and a sealing unit which prevents the damping oil from leaking to the rack gear hole, the sealing unit may comprise a ring-shaped sealing member which is tightly put on the outer circumferential surface of the piston body portion and a washer which has an outer diameter greater than the inner diameter of the rack gear hole, is put on the piston body portion to be located between the sealing member and the coil spring, and is pressurized toward the rack gear hole by the coil spring, and the sealing member may be pressurized toward the rack gear hole by the washer and received in the receiving groove. 
     The power adding unit may further comprise a second coil spring which elastically pressurizes the cam pusher to be in close contact with the cam and a spring support plug which supports the second coil spring in the housing, and the spring support plug may be configured to adjust the interval between the spring support plug and the cam pusher. 
     The cam pusher may comprise a rotation member which comes into contact with the outer circumferential surface of the cam and rotates with the rotation of the cam so as to reduce the friction against the cam. 
     Advantageous Effects 
     The door closer according to the present invention comprises a unit for adding door-closing force that is provided in the housing. Therefore, the door closer is smaller in size and lighter in weight. As a result, it is possible to mount the door closer to the door and reduce the risk of failure. 
     Moreover, even when a large spring is mounted to the inside of the housing to increase the elastic force, the door closer can be attached to the door such that the position of the link shaft is maintained a constant distance from the rotation axis of the door. Thus, the door can be opened 180° without having to extend the length of the link. 
     Furthermore, when the door closer is mounted to the door, the link shaft which is biased to one side of the housing can be located closer to the rotation axis of the door, thereby increasing the efficiency of the door closer. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view showing a door to which a door closer in accordance with an embodiment of the present invention is mounted. 
         FIG. 2  is a cross-sectional view showing the inside of a housing of the door closer in  FIG. 1 . 
         FIG. 3  is a longitudinal sectional view showing a link shaft in  FIG. 2  and a cam connected thereto. 
         FIGS. 4 to 6  are cross-sectional views sequentially showing the change of the inside of the housing of the door closer in  FIG. 2  while the door is closed. 
     
    
    
     MODE FOR INVENTION 
     Hereinafter, a door closer in accordance with an embodiment of the present invention will be described with reference to the accompanying drawings. The terminology used herein is for the purpose of properly describing preferred embodiments only and may be changed according to the intention or usage of a user or operator. Therefore, the terminology should be defined on the basis of the overall contents of this specification. 
       FIG. 1  is a perspective view showing a door to which a door closer in accordance with an embodiment of the present invention is mounted. Referring to  FIG. 1 , a door closer  10  in accordance with an embodiment of the present invention is attached to an upper surface of a hinged door  4  which is opened and closed by rotating with respect to a vertical rotation axis  7 . Specifically, a pair of flanges  12  are fixedly attached to a housing  11  of the door closer  10  by means of screws. One end of a link  15 , to which a pair of sticks are connected, is connected to an upper side of a door frame  2 , and the other end of the link  15  is connected to an upper end of a link shaft  20  which penetrates the housing  11 . 
       FIG. 2  is a cross-sectional view showing the inside of the housing of the door closer in  FIG. 1 , and  FIG. 3  is a longitudinal sectional view showing the link shaft in  FIG. 2  and a cam connected thereto. Referring to  FIGS. 2 and 3 , the door closer  10  in accordance with an embodiment of the present invention comprises a pinion gear  22 , a piston  25 , a first coil spring  33 , and a power adding unit  40 , which are provided in the housing  11 . 
     The pinion gear  22  is formed on the outer circumferential surface of the link shaft  20  and coaxially rotates with the link shaft  20  with respect to the rotation axis of the link shaft  20  which is in parallel to the Z axis. The piston  25  extends in the longitudinal direction of the housing  11 , i.e. in a direction parallel to the X axis, and is inserted into the housing  11  to reciprocate in the longitudinal direction of the housing  11 . The piston  25  comprises a rack gear portion  30  which is formed on one end thereof and engaged with the pinion gear  22 , a piston base portion  26  which is formed on the other end thereof, and a piston body portion  28  which connects the piston base portion  26  and the rack gear portion  30 . 
     The first coil spring  33  is a compression spring which accumulates elastic energy upon compression and is put on the piston  25 , specifically, on the piston body portion  28 . When the piston base portion  26  moves towards the link shaft  20 , i.e., when the piston  25  in which the rack gear portion  30  is engaged with the pinion gear  22  moves in the positive (+) direction of the X axis, the first coil spring  33  is compressed and accumulates elastic energy. At this time, the first coil spring  33  elastically pressurizes the piston  25  such that the link shaft  20  rotates in a direction that closes the door  4  (see  FIG. 1 ). 
     The link shaft  20  and the pinion gear  22  are located on one side in the longitudinal direction of the housing  11  (in  FIG. 2 , the right side of the housing  11 ), and the first coil spring  33  and the piston base portion  26  are located on the other side in the longitudinal direction of the housing  11  (in  FIG. 2 , the left side of the housing  11 ). The first coil spring  33  and the piston  25  can be arranged to overlap each other in the housing  11 , and thus the inside of the housing  11  can be configured compactly and can be reduced in size. 
     In the housing  11 , a first spring hole  13 , into which the first coil spring  33  is inserted, and a rack gear hole  14 , through which the rack gear portion  30  reciprocates and which has an inner diameter smaller than the inner diameter of the first spring hole  13 , are connected to each other in a line. The first coil spring  33  is inserted into the first spring hole  13 , and then the piston  25  is inserted into the inside of the housing  11  through the first spring hole  13 . The rack gear portion  30  passes through the first spring hole  13  and enters the rack gear hole  14 . One end of the first coil spring  33  has an inner diameter that decreases at the boundary between the first spring hole  13  and the rack gear hole  14 , and thus the movement of the first coil spring  33  in the positive (+) direction of the X axis is restricted. When the piston base portion  26  moves in the positive (+) direction of the X axis, the other end of the first coil spring  33  is pushed by the piston base portion  26  and moves in the same direction. Therefore, when the piston  25  moves in the positive (+) direction of the X axis, the first coil spring  33  is compressed, and when the piston  25  moves in the negative (−) direction of the X axis, the first coil spring  33  is expanded and restored. 
     According to the door closer  10  of the present invention, even when a large spring  33  is mounted in the housing  11  to increase the door-closing force, the door closer  10  can be attached to the door  4  such that the position of the link shaft  20  (see  FIG. 3 ) is maintained a constant distance from the rotation axis  7  of the door  4 . 
     In other words, the link can be fixed in a constant position to face the outside of the door at all times. Therefore, even when the length of the coil spring and the length of the link shaft are extended to increase the elastic force, it is not necessary to further extend the length of the link. 
     Therefore, it is possible to fully open the door  4  to 180° without having to extend the length of the link  15 . Moreover, when the door closer  10  is mounted to the door  4 , the link shaft  20 , which is biased to one side of the housing  11 , can be located closer to the rotation axis  7  of the door, thereby increasing the efficiency of the door closer  10 . 
     The door closer  10  comprises a damping oil which is filled in the first spring hole  13  and a sealing unit which prevents the damping oil from leaking to the rack gear hole  14 . The sealing unit comprises a sealing member  63  and a washer  60 . The sealing member  63  is typically made of rubber and has a ring shape that is tightly put on the outer circumferential surface of the piston body portion  28 . A U-packing having a U-shaped cross section may be used as the sealing member  63 . 
     The washer  60  is made of metal, has an outer diameter greater than the inner diameter of the rack gear hole  14 , and is put on the piston body portion  28  to be located between the sealing member  63  and the coil spring  33 . The washer  60  is located in the first spring hole  13  and pressurized toward the rack gear hole  14  by the first coil spring  33 . In the housing  11 , a receiving groove  18  having an inner diameter smaller than the inner diameter of the first spring hole  13  and greater than the inner diameter of the rack gear hole  14  is formed at the connection between the first spring hole  13  and the rack gear hole  14 , and the sealing member  63  is pressurized toward the rack gear hole  14  by the washer  60  and received in the receiving groove  18 . The washer  60  comprises an inner circumferential projection  61  which projects so as to push the sealing member  63  to the inside of the receiving groove  18 . Even when the piston  25  moves in the negative (−) direction of the X axis as well as in the positive (+) direction of the X axis, the washer  60  pressurized by the first coil spring  33  pressurizes the sealing member  63  toward the rack gear hole  14 , and thus the sealing member  63  is not separated from the receiving groove  18 , thereby preventing the leakage of the damping oil. 
     Moreover, an oil passage hole  27  is provided in the piston base portion  26 . When the piston  25  moves in the positive (+) direction of the X axis, i.e., when the door  4  (see  FIG. 1 ) is opened, the damping oil present at the first coil spring  33  in the first spring hole  13  moves toward a cap  36  through the oil passage hole  27  to delay the movement speed of the piston  25 , thereby reducing the impact due to sudden opening of the door  4 . Meanwhile, when the piston  25  moves in the negative (−) direction of the X axis, i.e., when the door  4  is closed, the damping oil present at the cap  36  in the first spring hole  13  moves toward the first coil spring  33  through the oil passage hole  27  to delay the movement speed of the piston  25 , thereby reducing the impact due to sudden closing of the door  4 . 
     The power adding unit  40  adds power to close the door when the door (see  FIG. 1 ) is opened and then closed. The power adding unit  40  comprises a cam  52 , a cam pusher  41 , and a second coil spring  49 . The cam  52  is fixedly connected to the bottom of the pinion gear  22  and coaxially rotates with the rotation axis of the link shaft  20  which is in parallel to the Z axis. The outer circumferential surface of the cam  52  comprises an arc surface portion  53  which is spaced apart an equal distance from the rotation axis of the cam  52 , i.e., the rotation axis of the link shaft  20 , a concave surface portion  54  which is spaced apart a distance shorter than the arc surface portion  53  from the rotation axis of the cam  52 , and a pair of projection corner portions  56  and  57  which connect the arc surface portion  53  and the concave surface portion  54 . A cam insertion groove  17  is provided in the housing  11  such that the cam  52  is installed therein, and the entrance of the cam insertion groove  17  is provided on the side facing the door  4 . 
     The cam pusher  41  is elastically pressurized to be in close contact with the outer circumferential surface of the cam  52 , and the second coil spring  49  elastically pressurizes the cam pusher  41  toward the cam  52 . The cam pusher  41  comprises a rotation member  42 , a support member  44 , and first and second guide members  46  and  47 . The rotation member  42  comes into contact with the outer circumferential surface of the cam  52  and rotates with the rotation of the cam  52  so as to reduce the friction against the cam  52 . The support member  44  supports the rotation member  42 . The first and second guide members  46  and  47  can move in a direction parallel to the X axis along a guide slot (not shown) formed in the housing  11  and guide the cam pusher  41  to move in a direction parallel to the X axis. 
     The second coil spring  49  is inserted into a second spring insertion hole  15  which is formed parallel to the first spring hole  13  in the housing  11 . One side of the second coil spring  49  is supported by a spring support plug  50  which is fixed in the middle of the second spring insertion hole, and the other side elastically pressurizes the cam pusher  41 . The spring support plug  50  is configured to adjust the interval between the spring support plug  50  and the cam pusher  41 . Specifically, the spring support plug  50  is screw-connected to the second spring insertion hole  15  and moves in the positive (+) or negative (−) direction of the X axis in response to the rotation direction and amount with respect to the second spring insertion hole  15 , thereby adjusting the interval between the spring support plug  50  and the cam pusher  41 . Therefore, it is possible to adjust the magnitude of the door-closing force added by the power adding unit  40  by adjusting the magnitude of the elastic force of the second coil spring  49 . 
     The link shaft  20  is biased to one side of the housing  11  in the longitudinal direction of the housing  11  (in  FIG. 2 , to the right side), and the second coil spring  49  is located on the other side of the housing  11  in the longitudinal direction of the housing  11  (in  FIG. 2  on the left side of the link shaft  20 ) apart from the link shaft  20 . Both the first coil spring  33  and the second coil spring  49  are disposed on the left side of the link shaft  20  (see  FIG. 2 ), and thus the inside of the housing  11  can be configured compactly. 
       FIGS. 4 to 6  are cross-sectional views sequentially showing the change of the inside of the housing of the door closer in  FIG. 2  while the door is closed, and the door closing operation by the door closer  10  will be described below by sequentially referring to  FIGS. 2 and 4 to 6 . First, the door  4  (see  FIG. 1 ) is closed in  FIG. 2 , and when the door  4  is opened, the pinion gear  22  formed in the link shaft  20  (see  FIG. 3 ) rotates in the counterclockwise direction, and as shown in  FIG. 4 , the piston  25  moves in the positive (+) direction of the X axis to the maximum. Referring to  FIG. 4 , the first coil spring  33  is compressed to its maximum, and as the cam  52  rotates in the counterclockwise direction, the cam pusher  41  comes into contact with the concave surface portion  54  of the cam  52  and then with the arc surface portion  53 , and thus the second coil spring  49  is also compressed. 
     Referring to  FIGS. 4 and 5 , when the power to open the door  4  (see  FIG. 1 ) is cancelled, the first coil spring  33  expands and elastically pressurizes the piston base portion  26  in the negative (−) direction of the X axis such that the piston  25  moves in the negative (−) direction of the X axis. Accordingly, the pinion gear  22  and the link shaft  20  rotate in the clockwise direction that the door  4  is closed. From the state of  FIG. 4  to the state of  FIG. 5 , despite the rotation of the cam  52  in the clockwise direction rotation, the cam pusher  41  is brought into contact with the arc surface portion  53 , and thus the second coil spring  49  is not further compressed or expanded. 
     Referring to  FIGS. 5 and 6 , when the door  4  (see  FIG. 1 ) is almost closed, the elastic restoration force of the first coil spring  33  is reduced to less than the time of  FIG. 4 , and thus the door-closing force is reduced. However, due to the rotation of the cam  52  in the clockwise direction, the cam pusher  41  sequentially comes into contact with the arc surface portion  53 , the first projection corner portion  56 , and the concave surface portion  54 . When the outer circumferential surface of the cam  52 , with which the cam pusher  41  comes into contact, is switched from the arc surface portion  53  to the concave surface portion  54 , the second coil spring  49  expands, and the rotation force in the clockwise direction of the link shaft  20  (see  FIG. 3 ) coaxially connected to the cam  52  is increased by the elastic pressing force of the cam pusher  41 . As a result, the door  4  is completely closed, and thus it is possible to prevent the introduction of foreign substances, gas, etc., through the door  4  slightly opened. 
     The invention has been described in detail with reference to preferred embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents. 
     INDUSTRIAL APPLICABILITY 
     The door closer of the present invention can be applied to various hinged doors of a house, apartment, officetel, etc.