BACKGROUND OF THE INVENTION A push-pull door which remains open after a passenger entered therethrough causes energy loss and contamination of an atmosphere of an air-conditioned room. In order to prevent such problems, various armless door closers for closing a door after a passenger pass therethrough have been developed and employed.

One of the conventional armless door closers is disclosed in Korea Patent Registration No. 263251.

Fig. 1 shows a perspective view of the conventional armless door closer, Fig. 2 an exploded view of the armless door closer shown in Fig. 1 and Fig. 3 a sectional view of the armless door closer shown in Fig. 1.

As shown in Figs. 1 to 3, the conventional armless door closer disclosed in the 251 patent includes a flow control part 20 which is incorporated with the housing 10.

A pivot shaft 30 is mounted in the housing 10 along the center line of the housing 10. A portion of the pivot shaft 30 protrudes above the housing 10 and a connecting member 14 is mounted to the protruded portion of the pivot shaft 30. The connecting member 14 engages with a door plate 11 and a frame plate 12 which are fixed to the upper portion of the door panel d and to the door frame f, respectively.

The pivot shaft 30 located in the housing 10 engages

with a piston 41. The piston 41 moves upwards and downwards according to the rotational movement of the housing 10.

The piston 41 includes a flow passage 44 which controls the fluid flow filled in a cylinder chamber by allowing and blocking the fluid flow. Below the piston 41, a spring 42 is located to provide an upward resilient force to the piston 41. The spring 42 is supported by a lower cap 47 which closes the cylinder chamber of the housing 10.

The flow control part 20 includes a channel 22 through which fluid flows in upward or downward direction and a control valve 21 for adjusting the amount of the fluid flowing through the channel 22.

The conventional armless door closer is assembled as follows. First, the connecting member 14 is mounted to the protruded portion of the pivot shaft 30 and then the frame plate 12 and the door plate 11 having a spline part 13 which engages with the housing 10 are engaged with the connecting member 14. Thereafter, a nut 15 is engaged with the pivot shaft 30, thereby mounting the armless door closer to the push-pull door.

When the door is open by a passenger, the pivot shaft 30 does not rotate and the housing 10 rotates with the opening door d. The piston 41 which is engaged with a helical portion 32 of the pivot shaft 30 moves in a downward direction and the spring 42 is compressed by the piston 41. The fluid filled in the cylinder chamber 46 flows through the fluid passage 44 into an inner chamber provided in the piston.

After the passenger passes through the door, the piston 41 moves in an upward direction by the resilient force of the spring 42. Since the fluid passage 44 is blocked by a check ball 43, the fluid filled in the inner chamber flows through a gap between the helical portion 32 of the pivot shaft 30 and the piston 41 and then flows into the channel 22 of the flow control part through an upper channel 45a. Thereafter, the fluid flows into the cylinder

chamber 46 through a lower channel 45b. The amount of the fluid flow is controlled by the control valves 21 located at upper and lower end portion of the flow control part, respectively, thereby adjusting the door closing velocity.

As mentioned above, the conventional armless door closer adjusts the door closing velocity by controlling the fluid pressure. However, since the flow control part 20 is incorporated with the housing 10 at the side portion thereof, the manufacture of the housing 10 is difficult.

Further, since the channel 22 of the flow control part 20 is long, minute flow control is difficult.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide an armless door closer wherein a flow control parts including a flow control member and a flow control bolt are installed inside of the housing, thereby facilitating the manufacture of the door closer and providing more precise flow control.

In accordance with a preferred embodiment of the present invention, there is provided an armless door closer which includes a housing, a pivot shaft installed in the housing, a portion of the pivot shaft being protrudes above a top portion of the housing, a piston engaged with a lower portion of the pivot shaft, the piston executing both a reciprocating movement and a rotating movement, a spring providing a resilient force to the piston, fluid filled in an upper and a lower cylinder chamber of the housing, a lower cap closing the housing, a door plate and a frame plate engaged with the pivot shaft in that order, comprising a piston connecting member installed at a lower portion of the piston, the piston connecting member selectively closing a throttle orifice through which the fluid flows, the fluid flow being generated by the reciprocating movement of the piston; a flow control member

installed at a lower portion of the piston connecting member, the flow control member having a flow passage formed in a lengthwise direction of the flow control member through which an adjustable amount of the flow passes from the upper cylinder chamber to the lower cylinder chamber; and a flow control bolt installed in the flow passage, the flow control bolt adjusting the amount of the flow by minute movement thereof.

In one embodiment of the present invention, the throttle orifice includes a check ball having a diameter larger than the smallest diameter of the throttle orifice.

In another embodiment of the present invention, the flow control member includes a discharge hole through which the fluid filled in the flow passage is discharged to the lower cylinder chamber.

In yet another embodiment of the present invention, the flow passage has a cross sectional area which is uniform at an upper portion of the flow passage and gradually increased at an lower portion of the flow passage, and an outer surface of the flow control bolt has a cone shape which corresponds to the cross sectional area of the lower portion of the flow passage.

In yet another embodiment of the present invention, the flow control bolt has an end portion which protrudes out of the lower cap and is screwed to an inner surface of the flow control member.

In yet another embodiment of the present invention, the piston has splines formed on an inner surface thereof, the splines engaging with a helical portion of the pivot shaft to make the pivot shaft rotate with respect to the piston.

In yet another embodiment of the present invention, a piston housing is installed around the piston and the piston has a serrated portion on the outer surface thereof and the serrated portion engages with a serration portion of the piston housing in a manner that the piston moves in

an upward and downward direction with respect to the piston housing.

In yet another embodiment of the present invention, an insert ring is provided in the housing in order to support the piston housing.

BRIEF DESCRIPTION OF THE INVENTION The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which: Fig. 1 shows a perspective view of a conventional armless door closer installed on a door; Fig. 2 depicts an exploded view of the conventional armless door closer shown in Fig. 1; Fig. 3 illustrates a sectional view of the conventional armless door closer shown in Fig. 1; Fig. 4 represents a perspective view of an armless door closer in accordance with an embodiment of the present invention; Fig. 5 shows an exploded view of the armless door closer shown in Fig. 4; Fig. 6 illustrates a sectional view of the armless door closer shown in Fig. 4, during the opening of the door; and Fig. 7 depicts a sectional view of the armless door closer shown in Fig. 4, during the closing of the door.

DESCRIPTION OF SPECIFIC EMBODIMENTS Preferred embodiments of the present invention will now be described hereinafter with reference to the accompanying drawings in detail.

Fig. 4 represents a perspective view of an armless door closer in accordance with a preferred embodiment of

the present invention; Fig. 5 shows an exploded view of the armless door closer shown in Fig. 4; Fig. 6 illustrates a sectional view of the armless door closer shown in Fig. 4, during the opening of the door; and Fig. 7 depicts a sectional view of the armless door closer shown in Fig. 4, during the closing of the door.

As shown in Figs. 4 to 7, the armless door closer includes a housing 100, a pivot shaft 200 installed in the housing 100 and having a portion protruded above the top side of the housing 100, a piston 300 engaging with the pivot shaft 200 at the lower portion thereof and being movable in upward and downward direction, a spring 400 for providing an upward resilient force to the piston 300, a flow control member 500 installed below the piston in a lower cylinder chamber where the spring 400 is located, and a lower cap 600 for closing the lower cylinder chamber at the bottom side of the housing 100.

Onto the driving portion 220 of the pivot shaft 200, a door plate 700 engaging with the door and a frame plate 710 engaging with door frame are mounted in that order.

Further, the door plate 700 is fixed to the housing 100 at the top side thereof and the frame plate 710 is fixed to the driving portion 220 of the pivot shaft 200. On the frame plate 710, a nut 720 engages with the driving portion 220 of the pivot shaft 200.

The housing 100 of the armless door closer includes a through hole 113 at the top side thereof. An upper side wall 111 and a lower side wall 112 are provided in the housing 100 which forms a step. The upper side wall 111 has a polygonal cross-section and the lower side wall 112 has a circular cross-section. The diameter of the lower side wall 112 is larger than the longest diagonal of the upper side wall 111.

The pivot shaft 200 is installed in the housing 100 and a portion of the pivot shaft 200 protrudes above the top side of the housing 100. The pivot shaft 200 includes

the driving portion 220 which protrudes above the top side of the housing 100 and a helical portion 230 having spiral lines which engages with the piston 300. An upper part 221 of the driving portion 220 with which the frame plate 710 is engaged has a hexagonal cross section. A shaft guider 210 is located on the boundary between the driving portion 220 and the helical portion 230 of the pivot shaft 200. A quad-ring 240 made of organic resin and a bearing 250 are mounted on the driving portion 220 of the pivot shaft 200.

The quad-ring 240 and the bearing 250 reduce vibrations and frictions which are generated while the pivot shaft 200 rotates with respect to the housing 100.

The piston 300 engages with the helical portion 230 of the pivot shaft 200 in such a manner that the rotation of the pivot shaft 200 makes the piston 300 move in upward and downward direction. The piston 300 includes a spline boss 310 which engages with the helical portion 230 of the pivot shaft 200 and a piston head 314 which has a larger diameter than the spline boss 310. Further, the spline boss 310 of the piston 300 includes spiral lines on the inner surface thereof which engage with the helical portion 230 of the pivot shaft 200. A serrated portion 312 which engages with the piston housing 320 is provided on the upper outer surface of the spline boss 310.

An outer surface of the piston housing 320 has a diagonal cross section and engages with the upper side wall 111 of the housing 100. An inner surface of the piston housing 320 has serrations formed along the lengthwise direction thereof.

The serrated portion 312 of the spline boss 310 engages with the serrations of the piston housing 320 and the inner surface of the spline boss 310 engages with the pivot shaft 230. Therefore, piston 300 moves in upward and downward direction while being guided by the piston housing 320 and rotates with the pivot shaft 230.

The spline boss 310 has a discharge hole 313 through

which the fluid is discharged to an upper cylinder chamber.

An insert ring 330 is installed in a groove located on the boundary between the upper side wall 111 and the lower side wall 112. The insert ring 330 keeps the piston housing 320 at its position.

The piston 300 further includes a piston head 314 which has an engaging groove 311. The engaging groove 311 communicates with spline grooves formed by the serrations of the piston housing 320. A piston connecting member 340 is installed in the engaging groove 311.

The piston connecting member 340 includes a center hole 341 through which the flow control member 500 inserted and a throttle orifice 342 through which the fluid passes in upward direction. The diameter of the throttle orifice 342 gradually decreases from the upper opening to the lower opening and a check ball 343 is mounted on the upper opening of the throttle orifice 342. The check ball 343 has a spherical shape whose diameter is smaller than the upper opening and larger than the lower opening. Therefore, when the piston 300 moves downward, the fluid flows in the upward direction through the throttle orifice 342 and the check ball moves upward by the flow of the fluid. Further, when the piston 300 moves upward, the check ball 343 closes the throttle orifice 342 and, thus, the downward flow of the fluid is blocked.

Below the piston head 314, installed is the spring 400 and the flow control member 500 is located in the spring 400.

The flow control member 500 includes a flow passage 511 which formed through the center line of the flow control member 500. The outer surface of the flow control member 500 is divided into three portions having different diameters, respectively. An upper portion of the flow control member 500 is inserted into the hole 341 of the piston connecting member 340 and an lower portion thereof is fixed to the lower cap 600.

Since the cross sectional area of the flow passage 511 is smaller than that of the throttle orifice 342, the flow passage 511 allows smaller amount of flow to pass therethrough than the throttle orifice 342. The cross sectional diameter of the flow passage 511 is uniform at the upper portion thereof and then is gradually increased at the lower portion thereof. The flow passage 511 communicates with the lower cylinder chamber through a discharge hole 512.

A flow control bolt 520 is provided at the lower portion of the flow passage 511. The outer surface of the flow control bolt 520 has a cone shape which corresponds to the shape of the flow passage 511 to thereby allow an adjustment of the flow amount. The flow control bolt 520 has spiral lines which are formed on a portion of the outer surface thereof. The spiral lines engage to an inner surface of the flow control member 500. A head 521 of the flow control bolt 520 protrudes out of the flow control member 500 and the flow control bolt 520 is rotatable with respect to the flow control member by rotating the head 521.

The lower cap 600 is installed at the bottom of the housing 100. The lower cap 600 includes a connecting portion 610 by which the lower cap 600 engages with the housing 100. The lower cap 600 further includes a bolt hole 611 through which the head 521 of the flow control member 520 is inserted.

The operation of the armless door closer in accordance with above embodiment of the present invention will be described hereinafter.

The operation of the armless door closer during the opening of the door is shown in Fig. 6. The pivot shaft 200 is attached to the door frame via the frame plate 710 and the housing 100 is attached to the door panel via the door plate 700. Therefore, the pivot shaft 200 does not rotate since it is fixed to the door frame and the housing 100 would rotate during the opening of the door. That is,

the pivot shaft 200 rotates with respect to the housing 100.

The piston 300 moves in a downward direction along the serrations of the piston housing 320 by the rotation of the pivot shaft 200. The quad-ring 240 and the bearing 250 prevent the generation of the vibration of an inner wall of the housing 100 and the friction between the inner wall of the housing 100 and the pivot shaft 200.

The spring 400 located in the lower cylinder chamber is compressed by the downward movement of the piston 300.

Then, the fluid filled in the lower cylinder chamber flows to the upper cylinder chamber through the throttle orifice 342 of the piston connecting member 340 and the discharge hole 313. The check ball 343 moves upwards by the pressure of the flow and thus the fluid flow would not be disturbed.

Therefore, the armless door closer operates as shown in Fig.

6 during the opening of the door.

The armless door closer operates as shown in Fig. 7 during the closing of the door. After a passenger pass through the door, no external force is applied to the door panel and, in the armless door closer, the spring 400 which was compressed by the piston generates upward resilient force. The piston 300 located on the spring 400 moves slowly upwards, thereby applying pressure to the fluid filled in the upper cylinder chamber.

The check ball 343 moves downwards by the pressure of the fluid in the upper cylinder chamber and block the throttle orifice 342.

Therefore, the fluid flows downward through the flow passage 511 of the flow control member 500 and then to the lower cylinder chamber through the discharge hole 512.

Since the flow control bolt 520 is installed at the lower portion of the flow passage 511, the cross sectional area of the flow passage 511 is much smaller than that of the throttle orifice 342. The upward velocity of the piston 300, therefore, is slower than the downward velocity thereof.

The pivot shaft 200 rotates with respect to the piston 300 along the splines of the piston 300. Since the pivot shaft 200 is fixed to the door frame, a torque is applied to the housing 100 in the direction of closing the door.

Therefore, the door panel connected to the housing 100 is closed without any external force. Since the amount of the flow during the closing of the door is smaller than that during the opening of the door, the door is slowly closed.

The closing velocity of the door can be adjusted by rotating the flow control bolt 250. By rotating the flow control bolt 520, it moves upward and downward minutely, thereby changing the cross sectional area of the flow passage 511. That is, the amount of the flow can be adjusted by the rotation of the flow control bolt 521, thereby adjusting the door closing velocity.

As explained above, the armless door closer in accordance with the present invention provides a simple configuration and facilitates manufacturing process since the flow control member and the flow control bolt are installed in the housing. Further, since the passage of the fluid is shorter than that of the conventional closers, the armless door closer in accordance with the present invention provides more precise flow control, thereby facilitating the control of the door closing velocity.

While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.