DOOR-HINGE DEVICE HAVING AUTO-LOCKING FUCTNION Technical Field The present invention relates to a door hinge device, and more particularly, the present invention relates to a door hinge device having an automatic locking function, which enables a door capable of being automatically closed by returning force of a spring once being opened, to be held opened in a state wherein it is rotated by a predetermined angle.

Background Art Generally, doors are divided into an opening and closing door which is employed in an entrance, a sliding door which is employed in a window, a turnstile which is employed in an entrance of a building or the like, etc.

Conventionally, in an entrance, there is employed a unidirectional or bidirectional door. A bidirectional opening and closing door is used at a place where lots of people come and go, and a unidirectional opening and closing door is mainly used at a place where a few people come and go, such as an apartment house, an officetel and a house. Performance and application of an opening and closing door is influenced by a functionality of a door hinge device which rotatably connects the door to a door frame.

That is to say, a door hinge device allows a door to

be returned to its initial position even though the door is repeatedly opened and closed in one direction or in both directions. The conventional door hinge device includes a housing, a threaded shaft and a compression spring. The housing is fastened, at an upper end thereof, to a door supporting bracket which is arranged at an upper hinge part of the door. The housing has a movable body which is disposed therein in such a way as to be raised and lowered only in a vertical direction. The threaded shaft has an upper end which is fastened to a door frame supporting bracket arranged at an upper hinge part of a door frame and a lower end which extends into a space defined in the housing and is threadedly coupled with the movable body.

The compression spring is compressed by the movable body which is rotatively raised by rotation of the housing due to door rotation. The compression spring produces returning force and thereby automatically closes the door when external force applied to the door is removed.

Another door hinge device which is disclosed by the present applicant in Korean Patent Application No. 2000- 1866, enables a door to be maintained in an opened status when the door is rotated beyond a predetermined angle. The door hinge device includes a pair of rotating balls which are arranged on a circumferential inner surface of a movable body in a manner such that they are located opposite to each other. A pair of spiral guide grooves are defined on a circumferential outer surface of a threaded

shaft in a manner such that the pair of rotating balls are respectively guided along the pair of spiral guide grooves depending upon a rotation angle of the door. A pair of horizontally extending grooves are defined on a circumferential inner surface of the housing in a manner such that the pair of horizontally extending grooves are communicated with upper ends of the pair of spiral guide grooves, respectively. If the door is rotated beyond 90°, returning force which is produced by the compression spring for the movable body, is controlled by the pair of rotating balls and the pair of horizontally extending grooves, whereby the door can be maintained in an opened status.

Disclosure of the Invention The present invention has been made in an effort to partially modify a construction of the above-described door hinge device disclosed by the present applicant thereby to maximize door opening/closing force and door-opened-status maintaining force, and an object of the present invention is to provide a door hinge device having an automatic locking function, which enables elastic returning force to be produced and thereby lets a door to be automatically closed when the door is rotated within a predetermined angle, and which automatically prevents the elastic returning force from being produced and thereby allows the door to be maintained in an opened status when the door is rotated beyond the predetermined angle.

In order to achieve the above object, according to one aspect of the present invention, there is provided a door hinge device including a housing, a threaded shaft and a compression spring, the housing being fastened at an upper end thereof to a door supporting bracket which is arranged on an upper end of a door and having a movable body which is disposed therein in such a way as to be raised and lowered in a vertical direction, the threaded shaft having an upper end which passes through the door supporting bracket and is unrotatably fastened to a door frame supporting bracket arranged on an upper end of a door frame and a lower end which is threadedly coupled with the movable body of the housing, and the compression spring being compressed by the movable body which is raised upon opening of the door and exerting returning force to the door upon closing of the door, characterized in that a pair of guide projections each having a predetermined thickness are formed on a circumferential outer surface of the movable body in such a way as to be oppositely located to each other; and a pair of guide grooves each having a predetermined axial length are defined on a circumferential inner surface of the housing in such a way as to allow the pair of guide projections to be respectively guided upward and downward therealong in an axial direction, and a pair of horizontally extending grooves are defined on the circumferential inner surface of the housing in such a way as to be respectively communicated with upper ends of the

pair of guide grooves, wherein, when the door is opened, if the housing which is fastened to the door via the door supporting bracket, is rotated beyond a predetermined angle around the threaded shaft, the pair of guide projections of the movable body are rotated in a horizontal direction relative to the housing, and thereby, compressive returning force of the compression spring can be controlled.

According to another aspect of the present invention, the pair of guide projections and the pair of horizontally extending grooves are formed and defined on the circumferential outer surface of the movable body and on the circumferential inner surface of the housing, respectively, while having a height difference between respective guide projections and between respective horizontally extending grooves, so as to allow the door to be rotated beyond 180°.

By the features of the present invention, if the door is opened, the housing which is fastened to the door by the medium of the door supporting bracket, is rotated around the threaded shaft which is fastened to the door frame by the medium of the door frame supporting bracket. At this time, the housing raises, in the vertical direction, the movable body which is threadedly coupled with the threaded shaft. Where the door is rotated beyond 90°, the movable body is rotated in the horizontal direction relative to the housing, and thereafter, the door is maintained in an opened status by the compression spring.

Therefore, the door hinge device having an automatic locking function according to the present invention provides advantages in that, when a door is rotated within a predetermined angle, elastic returning force of a compression spring is produced and thereby the door is let to be automatically closed, and, when the door is rotated beyond the predetermined angle, the elastic returning force is automatically prevented from being produced and thereby the door is allowed to be maintained in an opened status.

Brief Description of the Drawings The above objects, and other features and advantages of the present invention will become more apparent after a reading of the following detailed description when taken in conjunction with the drawings, in which: FIG. 1 is a partially enlarged perspective view illustrating a state wherein a door hinge device having an automatic locking function in accordance with an embodiment of the present invention is applied to a door; FIG. 2 is an exploded perspective view illustrating an entire construction of the door hinge device having an automatic locking function according to the present invention; FIG. 3 is a longitudinal cross-sectional view illustrating the door hinge device according to the present invention in a door closing position; FIG. 4 is a longitudinal cross-sectional view

illustrating the door hinge device according to the present invention in a door automatic locking position; FIG. 5 is a transverse cross-sectional view taken along the line E-E of FIG. 4 ; and FIG. 6 is a transverse cross-sectional view taken along the line F-F of FIG. 3.

Best Mode for Carrying Out the Invention Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts.

A door hinge device in accordance with an embodiment of the present invention includes a pair of supporting brackets 30 and 40, a housing 50, a threaded shaft 60, a movable body 70 and a compression spring 80. The pair of supporting brackets 30 and 40 are respectively fastened to upper ends of a door 10 and a door frame 20 in a manner such that they are partially overlapped with each other.

The housing 50 is fastened to a lower surface of the door supporting bracket 30. The threaded shaft 60 is inserted into the housing 50 and is fastened, at an upper end thereof, to the door frame supporting bracket 40. The movable body 70 is disposed in the housing 50 and is threadedly coupled with the threaded shaft 60 in a manner

such that it can be raised and lowered in a vertical direction and can be rotated in a horizontal direction at a raised position. The compression spring 80 has both ends which are respectively seated on a lower surface of an upper end of the housing 50 and an upper surface of the movable body 70.

One half portion of the door frame supporting bracket 40 is flushed with the upper end of the door frame 20, and is fastened thereto by means of a plurality of bolts. A polygonal hole 41 is defined through the other half portion of the door frame supporting bracket 40, which projects outward. One half portion of the door supporting bracket 30 is flushed with the upper end of the door 10, and is fastened thereto by means of a plurality of bolts. A circular hole 31 is defined through the other half portion of the door supporting bracket 30, which projects outward.

The polygonal hole 41 and the circular hole 31 are coaxially aligned with each other.

The housing 50 has the same center as the polygonal hole 41 and the circular hole 31. The housing 50 defines an inner space 51 which is opened at upper and lower ends thereof and has substantially a large diameter. In the inner space 51, the housing 50 is defined, on a circumferential inner surface thereof, with a pair of guide grooves 200 and 201 which guide the movable body 70 only in upward and downward directions. The pair of guide grooves 200 and 201 are oppositely positioned to each other. Each

of the pair of guide grooves 200 and 201 has a predetermined axial length.

Also, a pair of horizontally extending grooves 300 and 301 are defined on the circumferential inner surface of the housing 50 in a manner such that the pair of horizontally extending grooves 300 and 301 are respectively communicated with upper ends of the pair of guide grooves 200 and 201. Each of the pair of horizontally extending grooves 300 and 301 has a predetermined circumferential length.

The opened lower end of the housing 50 is closed by a cap member 52 which is threadedly coupled to the opened lower end of the housing 50. A wrench groove is defined on a lower surface of the cap member 52 which lower surface is exposed to the outside.

The movable body 70 is slidably inserted into the inner space 51 of the housing 50 to be slid upward and downward. A pair of guide projections 100 and 101 are formed on a circumferential outer surface of the movable body 70 in a manner such that the pair of guide projections 100 and 101 are slidably engaged into the pair of guide grooves 200 and 201, respectively. A threaded hole 71 is defined through a center portion of the movable body 70 in a manner such that the threaded shaft 60 is threadedly coupled with the movable body 70 in the threaded hole 71.

The threaded shaft 60 has a contour of a circular solid shaft. A smaller diameter portion 61 which has a

reduced diameter, is integrally formed adjacent to the upper end of the threaded shaft 60. The upper end of the threaded shaft 60 is formed as a polygonal portion 62 which passes through the circular hole 31 defined in the door supporting bracket 30 and is fitted into the polygonal hole 41 defined in the door frame supporting bracket 40. A lower end of the threaded shaft 60 extends in the vertical direction, is inserted into the inner space 51 of the housing 50, and is threadedly coupled into the threaded hole 71 of the movable body 70.

Here, while it was explained that the pair of guide projections 100 and 101 of the movable body 70 are formed in a manner such that they are positioned at the same height, it can also be contemplated that they are formed to have a height difference therebetween in a manner such that they are not interfered by each other when they are rotated upon opening of the door 10. In this connection, it can be envisaged that the pair of horizontally extending grooves 300 and 301 for guiding the pair of guide projections 100 and 101 in the horizontal direction at the upper ends of the pair of guide grooves 200 and 201 are defined to have the height difference therebetween in a manner such that the pair of guide projections 100 and 101 can be slidably rotated approximately by 350° relative to the circumferential inner surface of the housing 50 when the housing 50 is rotated.

The compression spring 80 surrounds a circumferential

outer surface of the threaded shaft 60. In this state, a lower end of the compressions spring 80 is seated on the upper surface of the movable body 70, and an upper end of the compression spring 80 is seated on the lower surface of the upper end of the housing 50. When the movable body 70 is rotatively raised by the rotation of the housing 50 upon opening of the door 10, the compression spring 80 is compressed. And, if external force which is applied to the door 10, is removed, the compression spring 80 produces returning force and thereby lowers the movable body 70 to its initial position.

Further, oil O is filled in the inner space 51 of the housing 50 to prevent the component elements from being worn out. In this regard, it is preferred that an oil passage is defined in the movable body 70 to allow oil to flow therethrough.

Moreover, while it was explained that the polygonal portion 62 of the threaded shaft 60, which is unrotatably fitted into the polygonal hole 41 defined in the door frame supporting bracket 40, it can be noted that the upper end of the threaded shaft 60 is unrotatably fastened to the door frame supporting bracket 40 through thread coupling or by the medium of conventional fastening means.

Furthermore, it can be readily understood that, by screwing or unscrewing the cap member 52 which closes the opened lower end of the housing 50, a moving height of the movable body 70 can be adjusted, and thereby, it is

possible to determine a rotation angle of the door 10, that is, a locking position of the door 10 after rotation.

Hereinafter, operations of the door hinge device having an automatic locking function according to the present invention, constructed as mentioned above, will be described in detail with reference to the drawings.

As shown in FIG. 1, if the door 10 is opened, the housing 50 which is fastened to the door 10 by the medium of the door supporting bracket 30, is rotated about the threaded shaft 60 which is fastened to the door frame 20 by the medium of the door frame supporting bracket 40. By this, as can be readily seen from FIG. 3, wall surfaces of the housing 50, which define the pair of guide grooves 200 and 201, push the pair of guide projections 100 and 101 of the movable body 70 to rotate the movable body 70. In succession, the movable body 70 is rotatively raised in the vertical direction while being threadedly coupled with the threaded shaft 60, as shown in FIG. 4.

Thereafter, as shown in FIGs. 4 and 5, if the door 10 is rotated beyond 90°, the pair of guide projections 100 and 101 of the movable body 70 get out of the upper ends of the pair of guide grooves 200 and 201 and are guided into the pair of horizontally extending grooves 300 and 301.

According to this, the movable body 70 which is raised in the vertical direction, is not rotated any more. Then, the pair of guide projections 100 and 101 of the movable body 100 are rotated in the horizontal direction relative to the

housing 50 in the pair of horizontally extending grooves 300 and 301.

At this time, other than the case of opening the door 10, the door 10 does not receive vertical elastic force by the compression spring 80, but receives slide elastic force. At the same time, due to biasing force which acts against wall portions defining the pair of horizontally extending grooves 300 and 301 by the compression spring 80, leftward and rightward external force is controlled, and thereby, the door 10 can be maintained in an opened status.

After that, if the door 10 is rotated to be closed, the housing 50 is rotated around the threaded shaft 60.

Then, when the pair of guide projections 100 and 101 of the movable body 70 reach the pair of guide grooves 200 and 201 the upper ends of which are communicated with the pair of horizontally extending grooves 300 and 301, the movable body 70 receives returning force of the compression spring 80. Then, the pair of guide projections 100 and 101 of the movable body 70 are slid along the pair of guide grooves 200 and 201 of the housing 50 thereby to return the door 10 to its initial position.

Industrial Applicability The door hinge device having an automatic locking function according to the present invention can be applied to a refrigerator door as well as a conventional entrance and exit door.